Yep, problems in Linux. This issue did not yet trouble me, but it did trouble my girlfriend... and already the second time.
Here is the problem:
Youtube videos do not work anymore. They are played at a too high speed. Normal audio files (mp3 for example) on the local computer also do not play anymore. They also seem to be played at a too high speed. Actually, in short, it seems that nothing works as expected when it is using audio.
If you recognise this, or a part of this, problem... then it might be worth to check the following:
Open the Sound control from the System Settings. Check at the Output tab that the output is using the Internal Audio Device. If not, then this might just be the problem!
Hopefully this posts helps somebody out there. At least it will help me the next time I have this issue!