I am having the same error as I see several others have - mine is a default upgrade from 3.6 to the current 4.0.1 version, and this is on my test forum, not my live community.

Warning: array_merge() [function.array-merge]: Argument #1 is not an array in [path]/includes/class_bootstrap.php(1146) : eval()'d code on line 7

Based on info in other threads - I have already disabled plugins that are not vb4.0 - and that does cause the error to go away - however it still doesn't display my forum correctly - it's a bare html-type text list instead of the vbulletin content table layout.

I deleted all incompatible styles after the upgrade, and doublechecked to make sure that the style called for in the ACP is default vB4 - and it is.

http://www.bestofboards.net/forum/