There may be a bug with 10.7 when assigning In's & Outs to external devices. My setup consists of a Warm Stereo Buss Comp on the master plugin chain. I use the Utility, I/O plugin for the In's and Out's, which are 5-6... except, Output 5-6 are 7-8.
Under Pro Tools, this is not a problem so I figure it's an LP issue?
Does anyone care to try?