On Monday, January 6, 2003, at 12:30  am, Thomas Miller wrote:
> I accidentally hit Ctrl+Alt+Esc when I meant to type Ctrl+Alt+F1.
> I discovered that hitting Ctrl+Alt+Esc crashes my system reliably,
> where "reliably" means five times in a row.

That's ddb, the in-kernel debugger. From the ddb(4) man page:
"... key sequences for each port that will activate ddb from
  the keyboard:
  [...]
  i386     <Ctrl>-<Alt>-<Esc>"

You can disable it by compiling a kernel using a kernel config
without options DDB in it, if it really disturbs you.

//joelw