I need a small modification to a visual basic program

I bought a program from an author about a year ago and the program has been working fine but just recently the program has stopped working. its basically a parental website blocker which modifies the windows hosts file to block websites from loading. when i click on block site a message comes up saying "access to hosts file denied". Personally i think it may be something to do with an update from Microsoft but not 100% Ive checked and the program is set to require admin to run, but for some reason its still now allowing me to block sites on Windows 7 64bit or XP? (and probably Vista). I need someone with knowledge of these things to look over the code and simply get it working again, its probably a very easy fix to do. as long as it works and blocks sites again im fine. I will need the source code and a fully working app at the end of this.