Error 500; Geeze they look bad! Fortunately they're usually harmless.
They occur when a process is interupted before it can be completed. This can have a variety of reasons but is usually temporary.
The first thing to do when you get an error 500, is try again.
If it still doesn't work, send us the error code on your screen and we'll investigate.
Remember though, these errors are usually temporary. While we're investigating an error 500 you may find a cheeky attempt works 10 minutes later, so give it a go!