Looks to me like an issue with a gallery or some mods that was installed.

I would suggest you check with whom ever you got the mod from to see what they have to say, you may want try it with the default browser if you have not already, also may want (Check first) un-install, see if you get any errors in the first step, if so report those errors to the mod maker, but DO NOT proceed to un-install, it may crash the SMF.!/?

if it can be installed try to in stall it again with the default theme and see if you get errors and id so report those, or any errors you may encounter!

good luck!

regards,
Maxx