Sony Vegas fails

Hi

I have DELL Inspiron 1525 (OS Vista)

A year ago i've installed Sony Vegas Studio Platinum 8.0 and it' been working great.

BUT recently i can not start it.  It comes to the sign "creating file I/O manager" and then Windows shows, that the program has stopped working.

I've checked the license agreement, reinstalled the program, reinstalled codecs, checked for viruses, installed another version, checked for updates -  nothing helps!

Please help me, because i really need this program for my job. Thank you!