Picasa (in gallery) not linked. Can't open picasa folders. How do I fix it?
This is a bit of a stab in the dark from stuff I've read, but here goes...

I believe that the uploading is done through the generic Android/Google/Picasa features but HTC have their own gallery app that relies on an additional plugin to display Picasa Web Albums.

Go to the HTC Hub app, settings -> sync and make sure you have the sync option checked for HTC Hub. If you don't have the latest version of the Picasa plugin then you should get a notification to download it, which might fix your issue.

If you do already have the latest plugin then double check under the Accounts settings that your Google account is set to sync with Picasa and that there isn't an additional sync option somewhere for the plugin itself.