You can delete the font list file from the Program FilesCommon FilesAdobeFonts folder and this will cause your system to rewrite the font list. As retrocity said renaming would be safer. The font file is adobefnt.lst but it might have a version number in it such as adobefnt07.lst depending on which version you are using and which past versions you have used. There could be a corrupt font or font reference since you last installed Photoshop and it might fix your problem.