off & on monitoring

[radionut]

I am using 1.2.6 on my Dell 1720 Laptop with Vista. I use the program to record scanner audio by connecting a patchcord from earphone jack on scanner to line in on laptop. When I turn on MONITOR INPUT I get red VU indication on the record side and some days I see green indication on the output side and can hear (monitor) the audio. On other days without AFAIK changing anything I only get the red indication and cannot monitor. This is very frustrating! Can anyone advise the cause and a solution (that does not include dumping Vista which is not really an option.)
Ron