I can only guess, but it seems the design of the 2001's is much like when you have a problem running Microsoft Windows and your computer "freezes up" or "throws a blue screen" etc, the best thing to do is to either reboot or do a complete shutdown and re-start the computer--this seems to clear out whatever the problem was(most of the time!). It seems that when you have some of these unexplained problems with the 2001 Volvo models, if you turn the engine off and/or get out and lock /unlock the car, this "reboots" the computer system and tends to clear out these odd problems--just like with Microsoft Windows.--This worked when I was having weird door lock, gas door lock, sunroof control illuminated switch, etc. problems a few months ago.

Anybody else agree with this observation????