T60 hangs when trying to do dual screen mode

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I use a port replicator with my T60 and I notice sometimes that when I try to do dual screen mode (with an external 17" LCD) and I happen to have many programs on at the same time, the computer freezes and I have to reboot.

Are there anyone else encountering this problem? I'm not sure if its because of my video card (X1400) or my port replicator causing this.

I just downloaded the latest BIOS (1.09a) and it still happens.

Any help will be appreciated. Thanks!