Hello,
I have been having trouble with my bosses PCs all year. He has Outlook 2010 + Google Sync. He has 2 PCs (1 XP & 1 W7) and an iPhone.
Our problem is that his sent items are disappearing from the 'sent items' folder. He paid for a tech to rebuild and try to figure out why this was happening. He couldn't figure it out, but we thought that he fixed the problem. This was approx 1-2 months ago. Just yesterday his sent folder with 400+ emails was empty again. Since he has google sync running, it synced the folders (as it should) so all sent items are gone forever. They are not in the deleted items folder.
The tech tried the steps located here
Just this morning, he said that he deleted an item from the deleted items folder and instantly his sent items folder was empty once again. I don't know if that actually had something to do with it, but to me it seems like an Outlook problem, not necessarily a google sync issue.