UA-1G interface MP3 files skip!!!

I purchased a UA-1G Cakewalk interface to use as an external sound card. I have a HP laptop ( Vista 64 bit) 4G ram. When I play midi backing tracks through my Sonar Home Studio 7 the sound is fine, but if I use a MP3 file it skips or pauses for a second. It only happens when I use the UA-1G interface. If I hook up my internal soundcard it doesn't skip. It has to be something with Media player. Has anyone else had this problem?? I've tried Asio drivers and every other setting I could think of. Thanks for any help!

Thanks for trying to help me, The bitrate of the MP3 file is 128 Kbps, I have the UA-1G set to default. As I said, this only happens when I play a Mp3 file, like when I take a break, I play music from my Media Player Library, or some of the songs I have downloaded are in MP3 format. When I use the headphone/internal sound card, it works perfect with no skips, but the sound quality is not as good. When I hook up the UA-1G they skip. I just noticed the settings on the bottom of the UA-1G, they are all set in the down postition. Could this be my problem?? The sample rate is set to 44.4khz, the 96 khz is set to playback, the input monitor is set to auto, and the rec source is set to digital.