[Coco] No "3 musketeers"

[Diego Barizo]

For some unknown reason (at least to me) my old CoCo 3, the first one I 
bought, refuses to do a hard reset when I press [ctrl][alt]+reset.
The result is the same as a regular reset. All programs stay in memory.
This same computer used to be able to hard reset, I remember seeing the 
"3 musketeers" years ago, when this was the only CoCo 3 I could access.
Any idea what might have caused this?
She (her name is TeReSa ;-) ) behaves normally in any other condition... 
except being a bit "freeze-prone", something I always blamed on a 86 GIME...

Diego