I experienced a similar problem some time ago, when using the Panasonic Recorder software. Like you, I turned off all other applications, including anti-virus software, but the problem persisted.
I thought that it might be due to the way the program actually records the data to hard disc, causing momentary interruptions in the data capture process. I tried the program on three different PCs, including a laptop and experienced the problem with different severity, on the PCs. I noticed that the onset of the problem always seemed to occur after about one minute of recording, at which time there appeared to be considerable hard disc activity - indicated by the Hard Disc LED.
I eventually overcame the problem on all my PCs, by using an alternative program for recording via USB - Goldwave ( www.goldwave.com
) This is an excellent professional Audio Editor program and you can download and evaluate it free, from their website. There may be alternative audio editors suitable for USB recording - I had a brief look at 'Audacity' but it doesn't seem to have a USB input facility. If any other forum member knows of a suitable program, I'm sure they will inform us.......