The following MSKB article provides the fix for this issue.
OL2000: You Cannot Customize Outlook Today After You Install Critical Update
813489 for Internet Explorer:
http://support.microsoft.com/default.aspx?scid=kb;EN-US;820575

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Jocelyn Fiorello
MVP - Outlook
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> Cannot customize Outlook Today on a laptop running 2000
> Pro.
>
> New install but will not allow any changes to the Outlook
> today. Will not even access page when click on
> customize. Any suggestions?