I Think I'm having some Leopard Issues

I've been getting the "this computer needs to be restarted, hold down the power button for 5 seconds message" and its just working rather spookily in general. Internet doesn't work very well (yet when i bootcamp to vista, everything works fine, it can't be hardware) and if i let it idle, it won't come out of sleep without a hard restart.

i was hoping the 10.5.1 update would fix things but i'm having issues still.

this sucks

any advice or fixes before i revert back to my Tiger Image (smart users back up, especially in the face of a new OS, word of advice, or my 2 cents, whatever you want to call it)