Can you give some more specifics as to the problem.  Also, what aircraft specifically are you having a problem with?  Do the default planes work still or is that gone too?

As foolish as it sounds, take a look in the texture folder to make sure that there are .bmp files in there.  I have done that a few times where I forgot to copy the contents of the folder.  Otherwise, I would just try to fully remove the plane from the folder and try to reinstall it.  I'm sorry that I am not more help.