asterisk users - Mar 2006 - Two dissimilar data only T1 lines possible in Asterisk?

We are trying to use two data only T1 lines from two different
providers with Asterisk 1.2.4.  We added a second Ethernet card to
our computer.  After making sure the card had network connectivity,
Asterisk could no longer contact a SIP provider we use.  Does anyone
have experience with using two data only T1 lines like this?