Firing S&S strobes with 5d MKII problems

I'm trying to help out a student with a new 5d mkII, S&S housing and dual ys110alpha strobes (Y-synch cord). We can't figure out how to get the strobes to fire. I think it is a camera setting issue, but I'm not a canon guy, so I'm pretty clueless. The only setting I can find in the menu related to external lights is the "external speedlite control" and I can't get to any of the sub menus because it say something to the nature of "Cannot access menu because you don't have a speedlite attached or it isn't on" even when the hot shoe is plugged in. We tried different camera settings (manual, aperture priority, etc), and with the strobes on slave and normal, reconnected everything... nothin'. Is there some sort of enable hot shoe option buried in a menu or something?

Thanks!

Chris

Assuming the bulkhead is OK (by checking all contacts with a current checker) and the camera fires with other external strobes, I can only see these reasons for this to happen:

- strobe batteries depleted/mistakenly placed;

- hot shoe connector not fully inside hot shoe;

- strobe set at "on slave" (this should be set to off if strobes are connect via sync cord);

Any luck?