alrockliffe

Hi having a bit of a problem of late with my collection of cassettes. When I leave them, usually overnight, the section of tape that was 'exposed' has been erased. What sort of radiation could be causing this? The machine is switched off at night and sited well away from any strong magnetic fields etc, apart from which, any cassettes that have been stored partially wound, lying in my drawer, have also been similarly affected. This is becoming increasingly annoying / worrying, and is happening now on a nightly basis, so any info would be greatly appreciated. Thanks, Andrew