General :: Having To Restart Ubuntu Several Times A Day

I hope someone can help me. Been using Ubuntu for over a month now (My first foray into Linux) and I love it...BUT I'm having an intermittent problem that seems to be getting worse:Ubuntu will be working fine....then I'll go to open a program (like Chromium or Thunderbird) and it won't open. If I already have Chromium open, it might become unresponsive. If I'm downloading something, it will start acting weird (Like last night- I was downloading c.600MB file and Ubuntu went into dysfunctional mode- and said it was downloading a 2006453 GB file!)

Also, when it goes into dysfunctional mode, any dialogue boxes that come up (like the shut-down confirmation box) will be blank- just pure white- with no text or buttons visible.I can't even run any terminal commands when this happens, to try and diagnose the problem, because either terminal won't open, or if it does, it will be blank like the dialogue boxes- i.e. the purple background will just be replaced by pure white, with no cursor or text).I'll then restart the computer when these things happen, and then I'll get the "The disk for /tmp is not ready yet or not present" and have to press "f: to fix it- then it will boot up and work fine- sometimes for the rest of the day...sometimes for 5 minutes.

Since I don't see anyone else complaining about such behavior, I assume the problem is with my 'puter or my installation? If anyone has any ideas, please help. I really don't want to have to switch to a different distro- as I love Ubuntu///and I don't want to have to reinstall - as I have it configured the way I want it and plus it's on a partition (Still need to keep Win-D'ohs around just for when I want to use Magicjack)This is starting to happen several times a day...HELP...can't. Go. On like this![My 'puter's specs: Compaq Presario SR2170NX P4 3.0Ghz 1G Ram 150GB HD -all I usually do these days is email and the web]