If a P4 command fails when Slick is trying to compare two files, it seems to ignore it.
If the first "p4 print" command succeeds, but the second fails, slick opens the diff window showing the higher revision file on the left and showing empty content for the lower revision file on the right.
The 2nd p4 print failed because I killed it. It takes a realllly long time to run because in Beta5 Slick is still setting the "PWD" environment variable to //depot/branch/..... instead of the local file path.