Most likely it is a resource issue.

It might be you are not running a sound card that can handle the playback while recording. Most computers and all laptops today use a integrated chip for sound, and while this is fine for playing back music or recording something, it seldom can do both at the same time for any period of time.

If you add to this that an integrated chip is also having to share system resources, it becomes even more promblematic.

My suggestion is to make sure you have the latest drivers for your sound device, and for Windows in general. I am able to record while play back using my laptop, there is a delay but not really noticable until it gets into the 18-20 minute range of recording.