My apologies, folks...been quite busy of late, and quite truthfully, I don't check in here as often as I should.
I applied a number of patches to the Photo Albums code today, as well as making a server configuration change that will likely address the "Forbidden" issue. Please follow up here if the issue persists.
The likely culprit, is a piece of security code that attempts to block access to the server from DoS (denial of service) attacks. From what I can see, this code is falsely blocking legitimate access when pages with large numbers of objects are displayed - specifically, Photo Album pages with many images. When this happens, the "Forbidden" page is displayed.
For now, I've disabled this security module, which is not ideal. However, if doing so results in no more problem reports, I'll know I'm on the right track. The security module is configurable, so if it is indeed responsible for the errors I'll re-enable it with higher tolerances in a week or so, and see how things go.
Thanks for your patience - I know this issue has been a PITA for quite a while.
Bill