Microwave blows fuse
The most common suspects are the high voltage transformer and the magnetron.
It's also possible you have a flaky door switch or loose door switch mount.
If you or a friend decide to work on it, we have *critical* safety, disassembly, and troubleshooting info (as well as a text file which helps in diagnosing and repairing door switch problems) at our site, which is linked at our listing here on FixYa: http://tinyurl.com/yzjozk
You can find helpful exploded view diagrams and order parts by entering your model number here: http://tinyurl.com/gv383