10G Grid Control Preferred Credentials

Running grid control on Linux RH 2.1
Have monitored nodes on Hp-UX Itanium, tru64, and linux itanium.

Recently done a host password change, updated preferred credentials in grid. Click the 'test' button, and it works for the linux target nodes. For the tru64 and Hp-ux I get

"Connection to host XXXXXX as user oracle
failed: ERROR: Wrong password for user"

Now, before some bright spark offers up the grand idea of typing in the right password, believe me, I have... several times in fact. There was a forum thread on metalink regarding this, but no response from oracle on it.

Any ideas people? Quite willing to have egg on my face if its not a bug and its me being utterly stupid!

Bazza