How are you scheduling your script? If you're doing via the at command, then you must remember that it will be schedule to run under the system account. You can try scheduling runas /user:domain\user ..., but I never got that to work sucessfully.

The easiest way is to schedule it using the task scheduler (via start->Control Panel->scheduled tasks->right click->new->scheduled task (or the Vista equivalent)) where it allows you to specify the domain\user name and password. That works for me.

Or, see the command schtasks /?

Update: The following command worked for me. Note: You will be prompted for your password. I've wrapped the last option for posting:

schtasks /Create /tn fred /sc once /st 07:55:00 
/tr "c:\perl\bin\perl.exe \test\junko.pl
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