This is from the developer's forum, dunno if it helps though...
If you encounter a problem where the application crashes or you receive an Error 400 every time you try uploading your contacts to Google, we ask that you fill in the following bug report and e-mail it to
jason@syncinablink.com. We will try to fix your problem as soon as possible. We may contact you for further information.
1) What device are you currently using? (iPod Touch, iPhone, iPhone 3G)
2) What firmware are you currently running on your device? (2.0, 2.1, 2.2)
3) What version of Sync in a Blink are you currently running? This information can be found on the very bottom right corner of the Settings page.
4) Are you using a regular Gmail account or a Google Apps Email account?
5) Are you syncing contacts through iTunes?
If so:
a) What application are you syncing your contacts with and what version (eg. Outlook 2003, Outlook 2007, Address Book, etc.)?
b) What version of iTunes are you running?
c) What operating system are you running and what version?
6) How did you originally get your contacts on to your iPhone? (Did you do an iTunes sync with outlook/Address Book/Gmail/Yahoo/etc.? Did you create them manually? Did you sync your contacts with Microsoft Exchange or MobileMe?)
7) Are you using Microsoft Exchange or MobileMe? If so, have you enabled the appropriate option in the settings?
8) In the settings for the app, have you enabled "Backup iPhone contacts" or "Backup Gmail contacts"?
9) Please explain your problem in as much detail as possible. Try to include steps to reproduce the problem and any details that feel may be relevant in solving the problem.
10) (Optional) If you are willing, please attach your backup CSV files of your Gmail and iPhone contact lists. This would be of great help. Most of the problems we've encountered are because of user data. By sending us your contact list, it greatly increases your chances of getting your problem solved! We promise not to share your information with any other 3rd party and we promise to delete the files from our systems once we've uncovered your problem.
Specifically we will need an export of your current Gmail contact list (ie. the list of contacts that made it over) and the CSV backup of your iPhone contact list. You can export your Gmail contacts by going to the Contacts tab in Gmail and clicking on the Export link on the right hand side. You can find the iPhone CSV backup in Sync in a Blink by going to the History tab, viewing the details of your first sync, and scrolling to the bottom of the screen.