Windows 7 fails to shutdown

Hi guys,
ive had some strange goings on with my pc recently..
Most recent being failure to shutdown, it gets to the shutdown screen, then seems to hang with the 'shutting down' and little spinning circle.. ive left it for over 30mins on 2 occasions to make sure it wasnt doing anything, but have to manually hold power switch for 5secs to make it shutdown, then on boot i get the 'windows did not shut down properly' message with options for safemode etc..
It has been slow to shutdown prior to this week, but only a min or 2,
Also, the past few weeks i had issues with SAS spyware scans.. those seem to hang/freeze during initial stage of scans.. a few re-installs seems to have sorted it but other scans reveal no malware/spyware or virus.
Only issue being with JRT (junk removal tool) recently this also comes up with small windows error box as it starts saying something about ERUNT folder & access denied, but JRT will continue its scan as normal & it completes it...

Just before the 'shutdown' problems im having this week, i was doing a manual windows update, which again hung/froze during the 1st files download (not install). i had to quit it after 30-40 mins, thats when i 1st noticed the shutdown problems.
I could not get back on windows update downloads again for 2 days, that also hung/froze when searching for files before i could click choose important/optional etc.. it didint get that far to display any drivers.
Also - sometimes when closing apps such as browsers, players etc.. i get a windows message - 'xxxx has stopped responding' etc, with options to wait for prog to respond, let windows find solution or close program etc.. which is weird as its usually when i click red x to shut down the program/app. i never see it during running things and all software seems to be in working order.
So my thoughts are that windows has been corrupted somehow..
windows 'mr fix' also froze, + the start up 'system repair' function (f8 on boot) also found nothing wrong.

Rest of drivers up-to-date a few weeks before these issues with no noticable problems after installs,
I installed a new m/b & cpu last month says i dont need any new drivers for that, bios is original, no other new hardware so dont think its anything hardware related.. (is why i have not listed anything)
i believe its just windows 7..

Temps seem fine.. currently been on over 2hrs, normal browsing drives/web etc.. no gaming or intense stuff.. and temps are at
CPU - 24'C
MB - 21'C
That seems extremely low with no special cooling gear onboard??
thats going off the m/b's Asus ASuite 2 software..
Task manager states that 2.24gig memory currently allocated, with explorer.exe, web browser, Av software, gpu and that Asuite2 software being the highest memory hoggers.. nothing seems excessive but i dont really understand all the memory kb's etc.. Commit, working set etc.. i not got a clue xD
So temps & memory seem ok..

so summary xD ..
how can i make windows shutdown properly again?? and how can i stop all the little niggles im getting with scans, downloads and the erratic behavoir of closing software down.