It's happened to a few people but I never had this issue.
To fix it you just need to delete your blockchain and the tx folder an start your client back up:

BACKUP YOUR wallet.dat FILE!!!!

1. close client
2. go to roaming folder (here's my path to it for example): C:\Users\Admin\AppData\Roaming\Guerillacoin
3. delete "blk0001.dat" - or something named similar to that
4. delete the folder "txleveldb"
5. start your client
6. let it sync
7. profit?