Hi there, I have a 2.4GHz Macbook Pro, 2GB memory, 160GB HD, OSX 10.5.4. All updates are installed, disk has about 90GB free. The system boots and generally runs fine, unless I open up seemingly random combinations of applications. The machine will nearly freeze up, spinning pinwheel and all. I can switch between application windows, but moving them is very slow and jerky. Sometimes I can close applications, but need about 5 minutes between hitting cmd-q and the application actually closing. Cmd-tab almost never responds. Inside any application that's open at the moment, I get the pinwheel, which comes and goes intermittently. I can't reboot the machine (at least I can't get a terminal up via Quicksilver, and clicking on the apple menu gives me no response.) I started running istat menus, which show me a maximum system cpu load of about 75-80% (usually around 40-50%), no serious disk IO, and no less than 400-500MB of free physical memory. I started leaving activity monitor open in anticipation of this happening, and sorting by either cpu or any kind of memory usage I get no clue as to what's happening. The only option is to power-cycle the machine, or to leave it sitting for several hours, in which case it will sort itself out and let me enter commands. Sometimes, I will be able to interact with applications again normally, but occasionally the system will seize up again. I mainly use Firefox, mail, transmission, office 2k8 and some programming tools, but I cannot find any combination to reliably reproduce the problem. I've run rember to test physical memory, and onyx to check disk structure and run all cleanup/maintenance jobs. System.log prior to the slowdowns yields no clues; console shows a lot of cryptic application error messages, but nothing that looks like it should be crushing my system. I can't hear any disk activity, the fan doesn't speed up notably, and cpu temperature hangs around 57C. I'm at a bit of a loss here; any hints as to what could be causing this would be appreciated. I'm used to systems becoming unusable, but normally it's for a maximum of about 5-10 minutes at a time while they figure themselves out, and if I have some monitoring tools running, they generally show 100% either cpu, disk or memory usage. Help?