Well, I've been trying to find the cause of this for about a week now, but no dice. The forum is really what our site is all about, so it’s very important that I resolve this issue.
After some topics in our CBB forums receive approximately 10 replies, the first pages becomes inaccessible to some users. According to reports the page is blank and the source is empty.

I however, am unable to recreate the issue, making it difficult to troubleshoot. It seems this only affects users when they are logged in, and again this is only some topics.

I've tried syncing the forum, but it does not seem to work.

Some related links:

Our discussion on this issue.

Corrupt Thread 1

Corrupt Thread 2

Has anyone else had this issue? I can’t find any helpful information on this through the search.

Edit:
We had the posts per page set to 20 and had the issue, we dropped it to 10 hoping it would help. No such luck.