I saw people asking about this type of error on several phpbb boards. The answers provided to these people for the most part were simply not the solution.
Warning: implode() [function.implode]: Bad arguments. in /home/jazzcss/public_html/cruise/includes/template.php on line 265
Template->loadfile(): File /home/jazzcss/public_html/cruise/templates/subSilver/profile_avatar_gallery.tpl for handle body is empty
Having had a similar error this morning and having searched for an asnwer and failed to find one I decided to post what I found was my problem on the off chance that it helps others.
Check the file permissions.
The problem for me was that the admin template files had, for some reason, become non readable for the "world" group.
CHMOD the template files as 755 (-rwxr-xr-x) and it should be fixed.
I hope this helps some unlucky soul as this was a frustrating problem for me, I'd not chmodded in error but the file permissions became incorrect somehow. With template caching some would not immediately discover what the error was and since the phpBB error is that the file is empty (as opposed to not being readable) it can get damn confusing.