Thanks for replying.
And very sorry for the delay in answering to your post.
I was out of town.
The "Enterprise Manager" is
Enterprise Manager 11g - Fusion MiddleWare Control (Version 126.96.36.199.0)
Following is the output of opmnctl status -l
After that deleted the .dat files from "\Oracle\Middleware\asinst_1\reports\server" as mentioned in following post
And restarted agent and report servers
Every thing seems to be fine as of now.
I shall check tomorrow again if the EMAgent consistently works fine.