Short story is that I have two instances of SQL7 (patched to sp2) running on NT4 where the server process works fine but the associated agent fails to start -throwing errors like this:

[298] SQLServer Error: 17, SQL Server does not exist or access denied. [SQLSTATE 08001].

All this started about the same time i updated IE and installed the 2.7 MDAC on one of the machines the instances run on.

In both cases it is possible to log in via windows authentication using the same account the server agents are attempting to run under. So it would appear to not be a password/account issue.

tried to start the agent by running this on the command line:
sqlagent -i <instancename> -c -v
and just got the same raft of errors.

further detail: both instances are running on a two node cluster, typically one on each node. Both are using the same NT account.
The account is part of a group which has full access to the registry (which the agent apparently needs to read to get login information?), but i took the precaution of giving that account explicit access rights.

there are no security messages in the security log that seem pertinent.

So... don't see why/how the IE and MDAC install could have caused this, especially not since the instance running on the other node of the cluster has failed as well. But the timing is suspicous.

Any thoughts other than reinstalling the databases? That would mean unclustering, recovering & assorted ugliness i'd like to avoid.