10.2.5 has a known issue with USB devices. Try unpluging all except keyboard and mouse.
try opening the panic log (/Library/Logs/panic.log):
If I am right it will look like this:
"Unresolved kernel trap(cpu 0): 0x300 - Data access"
"...Kernel loadable modules in backtrace (with dependencies):
com.apple.driver.AppleUSBHub(1.9.9f6)@
dependency: com.apple.iokit.IOUSBFamily(1.9.8)@
com.apple.iokit.IOUSBFamily(1.9.8)@"
For more infor on this issue
Apple