That was exactly what I was trying to do (except that high of a resolution on the tv)
I was able to reproduce everything down to the messed up screen upon exiting X, except one thing - my tv screen remained blank. Although I could move my cursor off the screen like there should be another screen there.
I think there is something weird with my combination of driver, kernel, and Xfree version, i've heard of others having the same problem with very similar configurations.
What version of XFree are you using?
What kernel version are you using?