Server Error in '/' Application error on Uploading same document again in Library

I am facing this unprecedented and interesting problem. I have made a sharepoint site (Record center) and I want upload doucment in the Library. Everything goes smooth but once I try to upload the document, which is already uploaded by me (or existing in the Library), I get an error : "Server Error in '/' Application".

Can any please suggest why it is happening... I checked in Library setting also, I don't any option like "duplicate files allowed = YEs/NO".

Appreciate your help!

thanks, Umesh