Is it only the contacts that will not sync? You can try using DB fixit to see if there is any corruption in the data, if the sync only stops on contacts while syncing. I would try this step first.
There may be database corruption causing the issue. Click on the following link for the program called DbFixiT. This program has a trial version that you can download and install on your Palm OS device. The trial version will scan for database corruption and then report the corruption. You can then find the records causing the problem and fix them yourself or you can purchase the program and have it automatically fix the records.
http://www.pimlicosoftware.com/dbfixit.htm
To install the program, set all conduits to "do nothing" except quick install or install if using Palm desktop 6.2.
After you install the program on the handheld, run the scan and also scan for Blobs in the calendar.
After you clean-up the database on the handheld, set the conduits in hotsync to handheld overwrites desktop and perform a hotsync.
I assume your previous T5 sync'ed ok and that you have all your data restored on the laptop. If you need to recover your data on the laptop, you can, provided you only sync'ed once when the data was gone.
There is an issue if you sync 2 dissimilar devices to the same username in Palm Desktop due to the differences in the model specs.
You can try a couple things in addition to the DBfixit option.
1. Export your data from Palm Desktop then create a new username in PD. Import the data into the new username (you can work with the contacts only since they are not sync'ing). This is a way to determine if the data is the issue or the previous username. Delete the hotsync username on your HH (I will provide the steps). Change the hotsync conduits to desktop overwrites Handheld and then sync. If the hotsync stops on contacts again there is probably corruption in the data and you will need to use DB fixit to resolve the issue.
Click on the following link to the kb.hpwebos.com webpage for the article regarding,
How do I change or delete the user name on my handheld?.
http://kb.hpwebos.com/wps/portal/kb2/common/article/33416
The best way to preserve your data is to export the data in each category in Palm Desktop to a separate folder on your PC.
Create a new folder on your PC somewhere that is convenient. Name it something like Palm Desktop Data. Click on the link below and follow the instructions on that page for the export procedure.
http://kb.hpwebos.com/wps/portal/kb2/common/article/28734_en.html
Make sure you select all for the range in the export window.
With the data saved in the folder you created, make a copy of that folder and save to a flash drive, cd-rw or external hard drive.
Anytime you make a change in Palm Desktop, export the data that was changed to that folder and save again to the external media.
With this process you can always import the data back into Palm Desktop anytime you have a problem with the data in Palm Desktop or if your computer/hard drive/device crashes.
2. Because you sync'ed to the same username in PD you may need to hard reset your device and rename your backup folder. Before you hard reset, make sure your data is backed up from PD using the export feature.
Go to http://kb.hpwebos.com/wps/portal/kb2/common/article/887_en.html and follow the directions to do a hard reset. Next before you hotsync your data back over you will need to rename your backup folder, to do that go here;
XP
C:\program files\palm or palm one\[hotsync username]\ and rename your backup
folder to backup.old
Vista
Start-->documents\Palm OS Desktop\[hotsync username]\ and rename your backup
folder to backup.old
Then hotsync to your current hotsync name and all your contacts, calendar,
tasks, and memos will come back over.
Show file extensions for XP or Vista
XP
If you can not view file extensions on your PC I would like you to open a
folder go to Tools-->Folder Options--> View (tab) and under show hidden
files and folders uncheck hide file extensions for known file types.
Vista
Open control Panel go to Folder Options--> View (tab) and under show hidden
files and folders uncheck hide file extensions for known file types.
You may need to hard reset your device and rename your backup folder. Go to http://kb.hpwebos.com/wps/portal/kb2/common/article/887_en.html and follow the directions to do a hard reset. Next before you hotsync your data back over you will need to rename your backup folder, to do that go here;
XP
C:\program files\palm or palm one\[hotsync username]\ and rename your backup
folder to backup.old
Vista
Start-->documents\Palm OS Desktop\[hotsync username]\ and rename your backup
folder to backup.old
Then hotsync to your current hotsync name and all your contacts, calendar,
tasks, and memos will come back over.
Show file extensions for XP or Vista
XP
If you can not view file extensions on your PC I would like you to open a
folder go to Tools-->Folder Options--> View (tab) and under show hidden
files and folders uncheck hide file extensions for known file types.
Vista
Open control Panel go to Folder Options--> View (tab) and under show hidden
files and folders uncheck hide file extensions for known file types.
For reference purposes, click on the following link for the support page for your device on the kb.hpwebos.com webpage.
http://kb.hpwebos.com/wps/portal/kb/common/article/47831_en.html#tungstent5
There are links on the page to the user guide, troubleshooting, how to's, downloads, etc.
, thought no problem had it backed up 
? Got a T3 when loaded took out all my info from laptop
, got a T5 now trying again but on desktop, seamed to work but the contacts keep on coming up with error and will not transfer on to new hand held, do not want to put them in by hand, any suggestions to get the computer and handheld to talk together.
