No application VoiceMailMain?!?

When I dial *98 and enter the mailbox number (801 in this case) it immediately hangs up on me. I’ve reviewed the console and don’t know where to go from here. I’m running Ubuntu Jaunty with packages from the repository on a SheevaPlug (ARM processor.) I’ve never seen an issue like it:

(debug mode)

Executed application: GotoIf
Launching 'NoOp'
Executed application: NoOp
No application 'MailBoxExists' for extension (from-internal, *98, 7)
Spawn extension (from-internal,*98,7) exited non-zero on 'SIP/850-00207070'
Soft-Hanging up channel 'SIP/850-00207070'

So, I decided to simplify things by creating a dedicated extension:

exten => *95,1,Answer
exten => *95,n,VoiceMailMain(801@default)
exten => *95,n,Macro(hangupcall,)

Here are the results of that endeavour:

Checking SIP call limits for device 850
Launching 'Answer'
SIP answering channel: SIP/850-001b02d8
Setting framing from config on incoming call
No application 'VoiceMailMain' for extension (from-internal, *95, 2)
Spawn extension (from-internal,*95,2) exited non-zero on 'SIP/850-001b02d8'
Soft-Hanging up channel 'SIP/850-001b02d8'

Voicemail is definitely loaded:

*CLI> show modules like voicemail
Module                         Description                              Use Count         Indicator for whether a voice mailbox ha 0               Comedian Mail (Voicemail System)         0         
2 modules loaded

The permissions on it:

root@pbx:/etc/asterisk# ls -l /usr/lib/asterisk/modules/app_voicemail*
-rwxr-xr-x 1 root root 150548 2009-10-08 17:37 /usr/lib/asterisk/modules/
-rwxr-xr-x 1 root root 138060 2009-10-08 17:37 /usr/lib/asterisk/modules/
-rwxr-xr-x 1 root root 125712 2009-10-08 17:37 /usr/lib/asterisk/modules/

I’m at my end - please help me!