Constant loss of connection with interface

Hello I have recently been having the issue of constant loss of connection with my interface and I'm not sure what the problem is. My interface is a digi003 rack, pro tools 10 LE, using imac OS 10.9.3, and I am keeping the hardware buffer size at it's highest for mixing and the connection still gets lost. The weird thing about it is that i will lose connection almost immediately after starting a session and then I will change the h/w buffer size from the highest number to the next number down and then it will reconnect. I'm using Superior Drummer 2 and Trilian in each session which take up space but it shouldn't be causing me this many problems. I'm sure there is just something small I'm overlooking but any help would be greatly appreciated. Thanks!