Encryption with expired key?

[Geraint Paul Bevan]

I am very new to gpg, so apologies if this is a stupid question. I've 
read all the documentation I could find, but haven't yet found an answer.


I have been given a key, which I have been assured works fine with PGP. 
However, if I try encrypting a file with it using the command:
'gpg --encrypt -r name file'

the encryption fails with the error message:

gpg: name: skipped: unusable public key
gpg: file: encryption failed: unusable public key

Looking at the key with --edit-key, it shows

pub  1024R/<number>  created: 2003-03-12 expires: 2003-03-12 trust: -/e
sub  1024R/<number>  created: 2003-03-12 expires: 2006-03-11

Is gpg giving me correct behaviour, or is this a bug? More importantly, 
how can I encrypt a message with this key?


Thanks in advance,

Geraint.