Embedded FLV glitches

Hi,
I am going mad with a really weird problem with embedded FLV. I have an SWC (exported by Flash CS5) containing several FLVs put inside different MovieClips, each one with a specific linkage.
When I link the SWC in FlashDevelop and instance the MovieClips containing the FLVs, sometimes it happens that the first 10-20 frames of the clip show terrible destructive glitches, sometimes a clip transform into another one too!
It looks like there are strange interactions between FLVs on scene: the clips onscene are 7 (small clips), and if played normally the show glitches, while if I substitute some of them (like 3) with MovieClips made of the corresponding PNG sequences, glitches disappears from the remaining FLVs!

I have tried an experiment too: I have a scene change that shows a fullscreen clip, and normally I should play it as soon as the previous scene completes, but if I stop it and add a delay before starting it, I see the first frame of a different clip, while when the clip starts I see the correct animation (sometimes with very big glitches anyway)! If I set a different frame with gotoAndStop(X) I can view frames from other clips too!

It looks like there is a very big bug in the FLV playback, as if FlashPlayer couldn’t manage FLVs loaded into memory correctly.