Ok, so one is embedding the images using URL's but says that the URL's tend to be extremely long with lots of encoding in them, plus a small amount of test, probably less than 500 characters.
The other is actually uploading the files.
I have asked for both to send me either the files or links the next time it happens so that I have examples and can test it myself. Unfortunately I have not seen any server log errors, but when I have more idea of the time I'll have a better idea of what to look for because I do seem to get some errors in the mornings but they are mainly related to e-mail notifications and I think that the host is most likely doing backups because of the consistency in the time frames, but because it is on a shared host they will not confirm it or give me any info related to system maintenance.
I'll be moving to a VPS when we actually go live in about a month and will have access to the web server logs then.
Should I open a bug report on the next occurrence or just go ahead and update this thread?