Dear Knoppix friends

Has anybody ever heard about Knoppix disabling a built-in modem?

I have used Knoppix 3.3 on a Dell 2650 with success
(also trying boot option toram, without success though).

Afterwards my built-in modem did not respond any more.
Diagnostic: "a signal tone goes into the modem but the modem cannot hear it".

Is this a coincidence or a hard to believe effect of Knoppix?