Playback problem..

I've got this really twisted problem when playing any divx/xvid, and if I don't find a solution soon i'm going to go insane.

Well, to the actual problem..
When ever I start watching any DivX/XviD with BSPlayer, or any other player, it starts just fine but then about every minute or so there is this perverted fastforwardy thing that last about a second. A bit like if you actually jump to a scene in a movie and the pictures a bit jerky for a while, if you know what I mean. And I guess you can think how annoying that is if someone was pressing fastforward for a second every minute during a movie.

I've tried absolutly everything, re-installed all codecs, tried different codecs, pretty much every version of DivX/Xvid/ffdshow and no help.
Even tried a few different graphic cards, and of course new and old drivers for them. Even re-installed windows just in case.

Oh well.. i'm pretty desparate right now so absolutly any advice and ideas are welcome how ever stupid it may be.

[Chumber]

PC fast enough?
Playback from HD or CD?
Enough Ram? Slow HD?

Just a few thoughts...