I'm having a strange issue with my Macbook Pro (15", unibody, removable battery). It boots to the desktop, after that it's very slow, and I can't open any programs. I can move the mouse, and make the dock appear and click on program icons, but they won't open. Finder works, as do the programs I have set to open at login. Occasionally, it freezes and becomes unresponsive for about 30 seconds, or until I reboot. After rebooting, it keeps doing the same thing.
That's an odd one. Here's some things you could try:
Slow speed and freezes could be indicative of a hard drive failure, so the first test should confirm or rule that out.
Next, if it's software related, the second should narrow down whether it's a software issue related to your log in, or if it's an overall software issue.
If it's the overall system, then we try the third and fourth idea. These last two will hopefully isolate whether it's a hardware or a system-wide software problem.