Oper or not to Oper

["Oliver Marshall" <om@xxxxxxxxxxxxxxxxx>]

I have setup an O line on my server and I can issue the /oper command at
any irc client and it says that I am an Operator of the server, but when
I perform an operator command, it cheerfully reports I'm NOT an
operator.

"
-
You are now an IRC Operator
-
Permission Denied- You're not an IRC operator
"

That was after doing "/oper <user> <pass>" then doing a "/rehash" but it
also ignores making people and myself ops of channels etc even though I
have done the /oper command.

Any ideas why that might be ?

Olly