why is my samsung captivate so slow after 2.2 upgrade?

Mine does the same thing and I have the same problem as you do, no one seems to know what to do to fix it.

I get a similar issue. It seems like things got alot slower after I upgraded to 2.2, and my phone is prone to constant hang-ups and the occasional (Or if it's the music player, inevitable) crash. If this is indeed the same problem, How would one go about redoing a flash?

I had the same issue after updating my Captivate to 2.2.  I contacted Samsung and they had me do a device recovery which seems to have worked.
Be fore doing these steps, be sure to back up your data as it will wipe all your info.

1. Power off the handset. 

2. Hold the Vol Down Key + Vol Up Key + Power Key for 15 seconds then release. 

3.When the recovery screen comes up, use the volume up key and volume down key to navigate through the selections and the power key to  select item. 

4. Select Delete all user data to recover the device. To confirm, scroll down and select Yes – delete all user data. The phone reboots and again  displays the recovery screen. 

5. Select Reboot system to restart the handset again.