i have a concern about the stability of the ELAN and my services provider feel the need to INI the 81C to clear some register problem.

i have been assured that no impact would be felt on the ELAN, but i seem to remember that at last the callpilot and symposium link get drop.

any body know of any other issues?

You should be able to do this with minimal impact to Symposium and Call Pilot, however, I have seen issues on a couple of occasions where we have had to reboot the Symposium and Call Pilot to sync them back up correctly, if you are using Call Pilot for announcements etc for Symposium. (Many of the services, although they looked to be working, were not, rather than individually restarting them, we went for the reboot to make sure we got them all)
After an upgrade to Symposium last year, we had issues of instability similar to what you describe, we had our vendor do another search on PEP's/updates/whatever else and they came back with several patches, that once installed, cleared up the issue immediately and it has never returned in over a year now.

I agree with trvlr1, should be minimal but may have to reboot SCCS and Call Pilot. Best practives say to take both system down and bring SSCs fully up first before starting Call Pilot. This is especially important if using ACCESS ports for custom script messages/greetings. If MLSM_service is not up the ACCESS ports may not come up.