I think the key routine (Run-Program-Run) will reset any "minor" faults. By cycling power to the processor (no matter what position the key is in) you are basically re-setting it to it's initial startup state. If the battery is good (which is a problem with the L55's) or if you have a memory...
90% of the problems with ControlNet are bad physical connections, make sure whoever installed the ControlNet Media did a good job.
2nd - it could be a firmware issue between CNB's on the network - Series A's don't play well with Series D's
3rd - RA had faulty T-taps for a while 1786-Tp**...
I am 99% sure that the L1 processor (now obsolete from Rockwell) only supports firmware 13.27 and lower. Your only real answer is to go back to your install CD/DVD's and install RSLogix5k version 13 then you can talk to the controller.
