Help needed.... newbie

Hi, sorry if these are newbie questions, any help greatly appreciated!
(1) Sound stutters and stops on playback
(2) Sound is muffled on deck 2 playback

Mairlist 4.4.11 is running on a Windows 7 PC with 4gb ram, intel quad cpu (q8400) and a soundblaster Live! 24-bit.
This is a home recording setup, I want to mix 3 stereo channels of music with an external mixer and a microphone.

Can’t anyone help with this enquiry? Do I need a different soundcard or just upgrade the software?

That version is very old indeed.

May I ask you to use the trial version of mAirList 6 and check if it happens with that one as well, so we know if it can be pinned down to that particular legacy version, or if it’s a general problem with the computer/setup.