The first time I can use Outlook 2003 normally.
After I close it and do some other work, I cannot open Outlook 2003 again.
I have to restart my computer, to be able to access Outlook again.

When you close Outlook does the outlook.exe process stop as well?
See http://www.howto-outlook.com/faq/outlookdoesntclose.htm

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Robert Sparnaaij [MVP-Outlook]
Coauthor, Configuring Microsoft Outlook 2003
http://www.howto-outlook.com/
Outlook FAQ, HowTo, Downloads, Add-Ins and more

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"scubadiver" <(E-Mail Removed)> wrote in message
news:5A4D7158-2B5B-48D6-ACB4-(E-Mail Removed)...
> The first time I can use Outlook 2003 normally.
> After I close it and do some other work, I cannot open Outlook 2003 again.
> I have to restart my computer, to be able to access Outlook again.

It maybe that OL is not closing properly
Look in Task Manager (Ctrl+Alt+Del) Processess Tab for Outlook.exe

If that is the case this is often caused by an addin or AV plugin

"scubadiver" <(E-Mail Removed)> wrote in message
news:5A4D7158-2B5B-48D6-ACB4-(E-Mail Removed)...
> The first time I can use Outlook 2003 normally.
> After I close it and do some other work, I cannot open Outlook 2003 again.
> I have to restart my computer, to be able to access Outlook again.