SLC5/02 communications problem

New guy 1st post so be easy..Yesterday I Installed a 550 panelview(2711-K5A2)tied to a slc 5/02. Today I made some changes(to the 5/02)--no problem. Later on tried to go on line it seemed to try then it said communications failed retry or go offline. Went to another machine and tried and everything worked--ok.The panelview is working flawless with the slc. I can't go on line.I'm using a PCMK card with a 1784-PVM4/B cable. Could the processer be the issue even though it working fine?
Thanks to all

1)restart your processor first

2) can you see processor on rslinx if yes
there should be no problem to go on line with PLC.

When you downloaded your changes, did you by accident, change your comm port setup?

I've done that before, and if you happen to click accept too quickly and miss the "apply communication changes" dialouge box and don't go online afterwards, you could miss it.

Yes I do see the processor & panelview in rslinx. Will do a restart later on today. If that don't work I'll try another processor. Thanks Terry