MacBook Pro freezes with beachball on login (OS 10.7 Lion) EDIT 8/21/11:  It appeared that this issue may have been fixed in Update 10.7.1, but it reoccured just recently.

Recently after upgrading to Lion, my MBP refuses to allow me to login.  I can see the screen and move the pointer, but the password box refuses any entry, and after about ten seconds my pointer turns into the beachball completely freezing up my mac.

I was able to temporarily fix the issue by upgrading my system from 4 to 8 GB of RAM which I already had on order, but after a couple boots, it has returned to it's unusable state.

I have researched some other sites, including the Apple Forums, but I haven't found any great solutions.  I'm wondering if anyone else has/had seen this issue, and knows of a good fix that I can utilize until Apple issues an update.  (which I will have to install somehow after logging in)

I have a 15 in, 2.4 Ghz i5 MacBook Pro from Spring 2010.  I dual boot with Windows 7 under bootcamp and I have a firmware password set.  Both instances of the freeze have seemed to occur after coming back to the mac side from W7.  I have regular time machine backups.
Disable Automatic Graphics Switching

EDIT:  In diagnosing the issue, you should update to the latest 10.7.2 update

After browsing the Apple Discussions Forums more thoroughly, it seems that disabling automatic graphics switching in the energy/power settings of system preferences seems to prevent the freeze.  

This forces the MacBook Pro to use the discrete graphics chip which will consume more battery life, but you can manually switch to the other chip using the utility, GFXCardStatus (http://codykrieger.com/gfxCardStatus) This should make the computer usable until Apple issues a fix in 10.7.1 or whatever is next.

Unfortunately, users may have trouble just logging into their system to change this setting.  Typing in the password quickly (before the freeze starts) worked for me, but you may have to boot into safe mode instead (hold down shift on boot).