Trouble with Windows Media Player? Is it Avast?

I have Windows Media Player 11. One day I opened a file with several mp3’s and clicked ‘play all’. I have done this hundreds of times, however, this time WMP read through all the mp3’s and began playing just one, seemingly at random. What has caused this and how do I fix it? I have been told that it could be a conflict with my anti-virus program. I, obviously, use Avast and have for a long time. Could this have been the result of an update to Avast? I have turned off Avast and WMP still does the same thing. Very frustrating!!
Any bright ideas?

Thanks

Welcome

What is your operating system and Service Pack level you are using?

Maybe your system is infected so download Malwarebytes’ Anti-Malware (MBAM) then install it and update its definitions then run a Quick scan and have it remove all it finds then post its log here:
http://www.malwarebytes.org/mbam.php

@ rick.young
The short answer is no, as avast doesn’t block, but scans and alerts to infection (when it would then stop the activity) and presumably that isn’t what is happening or you would have said.

Longer answer with questions:
What other security software do you have installed ?
As it could be a conflict, but even so if it were conflict then really it should appear that nothing works (blocking) rather than random selection of mp3s in the playlist.

What version of WMP do you have, older versions are vulnerable to exploit ?