Older digium tdm400p card, still work

i have setup up a trixbox test box with a tdm400p card that i bought about 3 years ago. i worked well in a couple other test systems. i have 1 pots line connected and when i make calls to the pstn it will ring once then go into a cracking noise like a bad speaker would make. when i dial into voicemail its clear. i have checked for irq conflicts and there are none. im assuming that this card being old has nothing to do with it? if anyone would like to take a peek via ssh i can send you the ip address with temp password, many thanks.