[ct-user] Voice keyer 1.6

[VE3DZ]

I have now V.K. 1.6 by SM3W up and running with CTWIN 10 for a few days.
Everything was O.K. until today I started to hear echo on my messages while
monitoring them. Echo is not constant and may appear randomly anywhere in a
message.
I tried to re-record messages - still same problem.
Tried to play messages when no other program was running (incl. CT) - did
not solve the problem.
The Microphone in PC's Sound Card is muted.
PC is old P120 laptop
Anybody has any idea why it's doing that?
Thanks.

Yuri  VE3DZ