Display dimensions wrong

Hello.

Since upgrading to Lion I'm experiencing a strange problem.

My MacBook Pro is used at home with Cinema HD 30" attached and lid closed. Every morning I disconnect the external monitor and take the laptop with me (without opening the lid). Now when I open my laptop at work I can't make Dock show up (I have hiding turned on). After further investigation I found out that the cursor won't stop at the bottom of the screen. Normally, when you position the cursor to the bottom you can still see a couple of pixels of it. Mine is going down even further, so I can't see any part of it. To make it show up on the screen again I have to move the mouse longer, than usual.

Display resolution, however, is detected properly. Switching to another one then back to native resolution won't help. Pressing "Detect displays" won't help either. Only after reboot the system treats display dimensions properly.

Is there a workaround for that?