I want to send a mix to my guitarist so he can track his guitars. So I then bounce a m4a for him, but just before I send it, I think, mmm... let's just check if it's ok. So I bring it back to my session only to find out, everything is flanging!?! Nothing is in sync! I don't understand. So I make more tests and this time bounce a mp3, m4a and aif only to find out that the .aif (16 and 24 bit) and .mp3 are in perfect sync, but not the m4a again. Wow! is this normal? Anyone ever noticed this before? Am I doing something wrong? Or maybe it's the (VBR) playing tricks? I don't know. Any comments?