What does 'A Runtime Error Has Occurred. Do You Wish to Debug' mean?

Sadly one of the most annoying messages IE can offer as it (on the face of it) is unhelpful....

What it is trying saying is either:

The app you ran tried to read or push data that is incorrect. e.g push 'x'kb to a buffer that is only 'x'-1 in size)

or

The web page you opened tried to push or read data that was incorrect. e.g. the Web page tried to run a command your browser doesn't understand, (old JAVA or active X plugin etc etc etc) or requested something you or they (it's a two way street) don't allow to be given.

http://support.microsoft.com/kb/822521

http://support.microsoft.com/kb/226342