XThread error!: SHOWTHREAD IN GALLERY

[ZiNgA BuRgA]

When you're adding templates, are you adding them to the Global Template set?
Also, ensure that you have no templates named gal_postbit etc in any of your theme template sets.

MyBB's forum permissions can be a bit whacky at first, but XThreads doesn't interfere with them, so perhaps double check that the search permission is disabled for all groups on the particular forum (all groups should have custom permissions assigned to them if you do this).