I've just installed the latest version of vBSEO on a new installation of vBulletin 4.2.0 PL2.
Since installing vBSEO, some attempts to submit a new post result in what looks like a blank post, i.e., no content.
The contents the member was trying to post are all there, however. If I click on Edit, I can see everything that was posted. If I click Cancel, the post remains blank, but if I click Save, the post is now fully visible as it should be.
I'm wondering if this is related to the scroll bars previously reported with Social Bookmarking enabled. As with that bug report, I am using the non-legacy version of the postbit.
Turned off that Social Bookmarking feature for now to see if the problem re-occurs.