... open just long enough to execute (no chance of seeing output or errors or warnings)

You need to add <STDIN>; to the bottom of all of your scripts - then the dos window won't close until you hit return :-)
Hmmmm ... but that won't work where errors are involved ....

I, too, have Vista (Business) running a number of perl builds (including Active Perls 5.8.8 and 5.10.0). Thankfully, I haven't yet struck such an issue. The thing is that *something* must have changed - are you sure that updates are not being downloaded and installed automatically ?

Mind you, if there is such an update waiting out there, then I'll probably cop it, too, sooner or later :-)

Cheers,
Rob