Launchpad really slow

I'm running Mac OS X Lion 10.7.4 (11E53) on a 2009 iMac with 8Gb of RAM and have just taken a SW update. On reboot I've noticed Launchpad running very slowly, as in around 8 seconds from clicking the dock icon to draw the first screen with a similar time to move between screens or exit.

Any clues as how to fix this?

It's not the only quirk of the upgrade - Spotlight isn't indexing the system.

An update

The system continued to behave very buggily until this afternoon when I decided to go in to Time Machine. Basically the machine hung so I powered down, waited a few seconds then rebooted.

Everything works fine now I've no idea what happened or how it became "fixed" but I'll accept anything that comes my way!