first off - the t-1 cards are fairly reliable - either the are working good or just plain shot
usually - is this a t1c or a t1/e1 card and what kind of circuit is installed ?
can you hook up to the rs232 port with an adapter and look directly into real time errors ?
also what is the cpu - if it is 64 /128 than you have to have a clock card on the backplane.