General Support: Images disappear but thumbnails still there

Have been using Plogger for a little while today, it does what I need so I started to shift over images from another package that doesn't do what I want.

I have used both the Upload and Import feature and everything worked well, with both thumbnails and images appearing in the new gallery.

Then, suddenly, the full images stopped showing. One minute they were there, the next they were didn't show anymore. If I try to "View Image" on the full picture I get the Forbidden error ("You don't have permission to access...")

I can understand if this occured overnight, when perhaps the webspace provider changed some setting. However this occured between batch imports of images. Suddenly, ALL the full size pictures were not appearing. They are still in the database, and the thumbnails still appear (both in the gallery and in the admin), however the full size images just wont show.

I've been in and played with permissions on the files and directories, confirming they are correct and even changing some to try and get pictures to appear (ie changing 644 to 755 to 777 in desperation). I understand Plogger doesn't play well with safe_mode, and I'm not sure what setting my server is in (I can't find anything to tell me in their admin section - a php_info would be nice! - and their Knowledge Base is useless), but if safe_mode is ON then why would Plogger work at all? Why would it suddenly STOP working between imports of images?

In desperations I went through and deleted all the images I had uploaded, back to what I had that worked. No good; still the full size images did not show.

This is quite frustrating. I've searched around the support forums and found people mentioning similar problems, and their solutions usually have involved safe_mode or file permissions, both of which I've eliminated. Does anyone have any new thoughts?