Crackling sound

Hi,Lately I've been seeing a strange problem with the sound I haven't experienced before. What happens is after loading an a/c or a helicopter no matter if it's a FSX default or addon after a couple of minutes the sound starts to crackle and especially in external views. Most of the times the problem have been most appearent when on the ground while it often has become better after t/o.I'm using a Soundblaster Audigy 2 ZS with the latest drivers and I don't see (hear ;)) this problem in any other situations other than in FSX so I doubt it's a HW problem.Anyone else experienced this problem?