Sony Ericsson Xperia X10 :: Google Sync / Contacts Not Transferred From Phone To Gmail

Because of several issues with SE sync, I am trying to use Google sync instead. However, this is also not working as expected: I wished to have all my phone contacts transferred from the phone to Gmail contact list. I started with an empty Gmail contact list. I enabled Google sync as described on the SE website. I don't know exactly what it does, but I also enabled Settings -> Data synchro -> Gmail (perhaps related to my e-mails?)

Result: Calendar syncs without problem. Contacts do not transfer from phone to Gmail
Second trial: I created a new contact "A" on GmailI created a new contact "B" on the phoneI ran sync
Result: Contact "A" synced successfully from Gmail to phone. No sync of contact "B" from phone to Gmail.
Third trial: I modified contact "A" on the phoneI ran sync
Result: The modification done on the phone did not sync to Gmail
Hints from the phone: When I try using Google sync for calendar, the sync icon shows for some seconds, before the date of last sync is updated. All ok. When I try using Google sync for contacts, the sync icon shows for 5-15 minutes. It then disappears, but no date of last sync is added. When I check the contact list, contacts have been synced from Gmail, but not to Gmail.

When I select Settings -> Data synchro -> Gmail, the sync icon blinks for some seconds with a yellow warning triangle. I don't know if this is related to my Gmail e-mails. The e-mails in the Gmail app are loaded without problem.I have already tried going to "manage application" and clear data for "Gmail" and "Gmail storage". I should probably mention that I synced my phone contacts with Gmail some months ago, without problems. This means that my Gmail contact list was not empty when I started messing with this. However, on my first sync attempt, contact lists on the phone and on Gmail were not synced. Instead, all Gmail contacts were added to the phone, causing 95% duplicate entries. I exported my Gmail contacts, deleted the entire Gmail contact list, and synced again to remove duplicate entries from the phone. Then started the process above. I would rather avoid deleting all the contacts from the phone to reload them from Gmail or SE sync, because addresses, facebook/twitter connections, etc. do not sync well.