Strange neomail issue

[jerrypr]

A user of ours is reporting:

> (404) Not Found
>
> The server was not able to find the document (./USERNAME/neomail.pl) you requested
> Please check the url and try again. You might also want to report
> this error to your webhost.
>
> cpsrvd/9.9.8 Server at www.DOMAINNAME.com

when trying to read a particular message.

For a different e-mail account in the same hosting account, it works fine.

Squirrelmail works for both just fine. I'm not sure what logs to dig in. I browsed
the forums a bit, but nothing is sticking out.

Any ideas?

Thanks,
J.