If all you did prior to having the problem was add new templates (do you mean a new style?) and a different .htaccess, then try temporarily removing the .htaccess and see if that fixes it or try creating a new style with no parent:
- Styles & Templates > Style Manager > Add New Style
- Parent Style: No Parent Style
- Title: Default vBulletin
- Allow User Selection: Yes
- Save
See if that fixes the issue.