Freezing up & internet wireless connectivity

Hi My (3year old) Sony Vaio Z VGN is starting to develop a number of issues, and altho still functioning adequately, 3 of them are really starting to peev me!
1. Whether left open unattended or lid closed, thruout the day and night, sony will freeze up with blank screen and seemingly on full fan power. At night this will eventually drain the battery and shut down the computer anyway, but with warning signs coming up upon restart that a problem had caused it to shut down. At other times when on AC, the sony will just freeze up and needs to be restarted again, even tho it hasnt switched off.

2. Has worked with wireless conectivity before, but not now, as only works with ethernet cable plugged in. Wireless connection light (green) is on, but nothing happening.

3. When connected to internet and downloading stuff windows boxes regularly come up stating that i have lost contact etc with internet, internet is restarting etc, even though i am still dowloading ok, but have to go thru all the boxes, closing them off and getting back to the pages i was on - very annoying!

any ideas appreciated! Rob