Sound Blaster Live 1024

I have had this card for about 3/4 Yrs.

I have connected a VCR to the line-in that goes through a video/audio
switch box. (i.e. the video chanel goes through to a TV card, and the
audio outputs go to the line-in on the card)

I have noticed that if I leave my PC and VCR off for a while and then
boot up and switch the VCR on I get a horrible buzzing noise
on high volume.

The strange thing is if they go into the PC Mixer, and select recording
and change the recording input to mic (or something like that) then go
back to Line-in: the noise dissapears!

Then I can't get the noise to come back unless I leave my PC off for a
while.

I think it may be something to do with the card intially over amping
the signal. But I wasn't aware it would do this. I have the latest
drivers installed from Creative. Anyone have any ideas?