As Hellstorm asked, what was the initial interruption? and at what stage of the build did it occur?
without knowing the answers to those questions...
I would recommend you strip the entire unit,
Rebuild it step by step making sure all cables are correctly and securely placed,
check your psu fuse (in the wall plug) and if you have a multimeter, test the lines for current or if you have a known working psu handy, use that one to find out if its a psu related problem,
there is a breadboarding guide on the homebuild section that will help guide you through some fault-finding processes, that should help as well.