My machine is a 2010 Mac Pro 2 x 2.66 6-core intel xeon with 32 GBs of ram running Mac OS X 10.8.3. Just the other day it started to beach ball after about an hour of use. It doesn't make any difference what I am doing on it whether it be CPU intensive or the machine is just idling, without fail after an hour goes by it starts to beach ball and becomes totally unresponsive. I let it sit for an hour the other day but it just kept beach balling, so all I can do is hold the power button to shut it down and then restart it, but after an hour the same thing happens again. I have had this Mac Pro for about a month and a half now and everything seemed to work really well up until a couple of days ago. The computer is running a 30" and 20" apple display and it has the ATI Radeon HD 5870 1024 MB, also my hard drive is a Crucial M4 500gb SSD, I have it installed with APRICORN VEL-SOLO-X2. If anyone has any ideas what could be causing this please let me know.
I found the CULPRIT, my SSD needed a firmware update. Crucial Offers Firmware Update For Crucial m4 SSD BSOD
I would start with running
If it's an infrequent issue (and it is cured 100% of the time from a reboot), it's more of a resource exhaustion / rare bug and having detailed sysdiagnose snapshots is even more invaluable for teasing out what part of the software stack is getting stuck and causing the Finder / UIServer to mark the cursor as non-responsive.
The next time this happens, press the shortcut and start seeing if the logs can help you.
Eventually, a Finder window will open showing the sysdiagnose report - or you will pull the power / forcibly shut down the Mac. Just knowing it was blocked to tight to not even be capable to run sysdiagnose is valuable troubleshooting information.