Tagging Problem

Here's my wierd problem - sorry to sound like a noob:

I will update a file (using save tags) with the correct mp3 tags. When I view the file from WinXP, Mp3tag, or using a tag viewer - everything looks correct.
However, whenever the file is played in any media player, the incorrect old tags are displayed.

When I right click the file in any of my media players and view the mp3's tags using the built-in viewer, it still shows the incorrect data. However, when I view the ID3v1 and ID3v2 tags using the same players, it shows as the correct data that I tagged them with.

This is happening with all of my media players and most of my programs that read mp3 tags. What is going on?

Please name the programs that don't show the new tags.

Let's see...

Programs:

XMPlay
WinAmp
MusikCube
Foobar2000
Music NFO Builder
Nero!

I could give more examples, but I ran out of steam.

Maybe the old information is stored somewhere in the programs music library/database/whatever.

You can send me one of the offending files and I'll have a look if something is wrong.

Best regards,
~ Florian