Outlook uses over 1 GB RAM

I run Outlook 2003 against an Exchange Server

The problem is that the last days Outlook has been very unstable I have got messages like “Out of memory” and slow respons from the system.

Today I checked the processes and found out that Outlook use 1,4 – 1,5 GB (yes Gigabyte!) of memory when it’s active. As soon as I minimize Outlook it goes down to a more normal 20 – 30 MB.

Any idea of what the reason can be?
Is there any maximum size of the Archive files?