My hardware is a JS21 IBM server with AIX 5.3L. I can console into the blade but at times I am able to telnet to a LDAP server on port 389, but then there are times I can not telnet to the port. I can't ping the server when I experience this issues. My application I support goes down in flames and the users complain. I am able at the same time to telnet to the server from a different blade. Could anyone please let me know where to look for errors or troubleshooting steps -Thx 
Have you tried looking at the system log or the log for the network device/switch it is attatched to(in this case the blade center as well)? It sounds like your blade is dropping off the network.
Cheers,
Keith
Also confirm you are using the default ethernet packet type for IPv4 (not using SNAP).
When it does fail, check to see if the port is listening:
netstat -an | grep 389 | grep LISTEN
You should see an entry that says LISTEN. If you don't, check that the process is up and running.