Serious listener problem - can anyone help?

I've been working on a listener problem all day. Because there is quite a bit of evidence, I've posted the problem on my blog at http://t.co/ss0KHSbfSd - if you care to take a look and make any suggestions back here, I'd be very grateful!

The link above is a short form of
http://qdosmsq.dunbar-it.co.uk/blog/2013/05/this-listener-problem-is-driving-me-mad/ - in case you are suspicious of short form links.

In summary, a database is running and so is the listener.

$ . oraenv<EOF

orcl11g
EOF
$ sqlplus user/password

...
SQL> select 'It Worked!' from dual
...

However, connecting via the listener results in carnage:

$ . oraenv<EOF

orcl11g
EOF
$ sqlplus user/password_at_orcl11g

ERROR:
ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist Linux-x86_64 Error: 2: No such file or directory Process ID: 0
Session ID: 0 Serial number: 0

I have Googled and MOS'd until I'm blue in the face. Just about everything says to start the database. Or, relates to a RAC SCAN - and this is a single instance database, no RAC in use.

Appreciate any info, as it is, driving me mad! However, please don;t respond until you have seen what I've already done at the above URL. Thanks. (And sorry! But I know someone will tell me to make sure ORACLE_HOME in listener.ora is correct and such like, trust me, I've been and done all that. I resolved this error yesterday on another server by exactly that method!)

Cheers,
Norm.

-- 
Norman Dunbar
Dunbar IT Consultants Ltd

Registered address:
Thorpe House
61 Richardshaw Lane
Pudsey
West Yorkshire
United Kingdom
LS28 7EL

Company Number: 05132767
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