All the replication stopped in all 4 instances of SQL Server 2000.
I checked SQL Server Errorlog and also Event viewer. This is the only error message I can see everywhere.
"The replication agent is not registered properly. Rerun SQL Server setup".
Checked all the files in /com directory,binaries and dll's. Everything looked fine.
After spending lot of time in trying to solve, i failed . According to my analysis on this issue, I came to a conclusion , its looking for a specific file/dll/some registry entry which is missing suddenly/corrupted.
Since this is a critical one, I tried a different approach to solve this as a last option before going for reinstalling all SQL Server instances and restoring databases , which will be a real pain.
I created a new instance on the same server so that the new installation will overwrite all files/dll's/binaries ... whatever may be (or) recreate any missing files.
So after creating a new instance and starting all services, all the replication started working. Cool!! It worked. Thats wonderful. So, what I guessed was right.
So I can suggest people to do the same if they come across the issue in SQL Server2000. Quick and easy way. I uninstalled the newly created instance again.
Before this issue, what was the latest configuration for your sql server ? Which sp are you running - and did you reinstall the sp are you created the new instance ? Was there any change to your sql server configuration before this started ? Did you just have to create the new instance only on 1 server or all 4 (since you had problems with all 4) ?