sounds like the secure temp folder is full.
bring up a registry editor to find out where outlook stores the data.
it can be found in this key.
HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Outlook\Sec urity
its usually in the format of:
C
Documents and
Settings\<yourusername>\Local Settings\Temporary Internet
Files\<securetempfoldername>
empty the contents of the folder and away you go.