I've had *exactly* the same issue - particularly, though, I noticed that this was *only* happening when browsing through private galleries. For instance, if I go through my publicly shared folders, the google+/ twitter/ facebook menu bar appears under each picture without problem; it's only the private ones that seem to cause issues.
And yes, I did notice that the html code for the sharing feature was in place on any private pages. I had also tried compatibility mode and looked at this in few browsers, but got the same behaviour in all (IE9, Firefox 14, Safari 5, Chrome 20). This is a particular problem for me, as I run photostation over secure http. I believe that the sharing feature causes an "insecure content" error message in all browsers, though at the moment I can't see how to fix this problem.
I can understand this behaviour to a degree, if it *just* limited to private folders - I can see why you might not want to include the potential for publicly sharing a file that has been marked as private, but I get the impression that you see this in all instances, not just for private folders.
Could you confirm that your behaviour is identical to this? I'd be grateful if you could let me know, as I'm beginning to wonder if there isn't some script in the photostation web pages that verifies credentials, and it might be this that causes this (and a list of other credential related) problems.
The QNAP support page is at:http://www.qnap.com/en/index.php?lang=en&sn=4574
Whilst I have already raised this as an issue with QNAP, it would probably be a good idea to lend further support to this problem.