Turn off your vbulletin hacks in your vb plugin system and see if it appears Then if it does you need to turn on them one by one to get the offending one. Your have a conflict with a vb hack maybe like vbspell etc.
Have you disabled your vbulletin plugins and any hacks you have done like vbspell etc. All those plugins will break the comments box in vbulletin? You can send me an admin login via PM if I understand your english there and I will have a look.
I am not the developer of Photopost Pro only Reviewpost and Classifieds so I can not say what features any new features it would have. We just released 6.02 a few months ago and any new version would most likely be 6.1 when it came out.
The only time I have ever seen in support the comments box show up as a little pixel that means a hac conflict. Once the customer disabled any plugin or hack that might affect the comments box the problem disappears.