mail will not open

When clicked, Mail bounces twice but does not launch.

I have read (& followed) several other threads about how to resolve a similar issue, but without any luck. Aaargh.

- Running iMac 10.6.8

- have installed the update combo v1.1

- have installed the security update 2012-004

- mail 4.6

- only one version of mail, correctly sitting in library/applications

the only console message is

“22/10/12 11:39:38 [Mail] Unable to load nib file: MailViewer, exiting”

“22/10/12 11:39:38 …hd.peruser.501 ([0x0-0xfa0fa].com.apple.mail]) Exited with exit code: 1”

no user diagnostic reports

no system diagnostic reports

Any ideas about what else I can try?

Thanks.