Originally Posted by Chuck S
Yep you always need to input the correct information.
If says leave blank if blank or default meaning your forum tables do not use a prefix.
The default for Invision, if left blank during an Invision installation, the prefix is "ibf_".
I checked my friends older Photopost Classifieds... he too uses Invision, but 2.6 of Photopost Classifieds. His prefix in his Invision tables is also "ibf_". Looking at his Photopost setup in admin, Photopost shows "blank"... so it looks like leaving it blank worked in the past, but required inputting the "ibf_" sometime after 2.6x.
None-the-less, it's working now.