Oblivion Elder Scrolls 4 Visual C++ Runtime Error ???

ive had elder scrolls 4 and its 2 expansions knights of the nine & shivering isles latest patch etc an it has worked great for 2 months until 2 days ago when out of the blue it crashed during game play .

my system specs are

PB5 mother board
2 x 1gb OCZ gold edition 800mhz in dual channel
E6300 @ 1.86 ghz
leadtek 7950 gt 256 bit 256 mb
500 W psu
Win XP home 32 bit
Sond max HD audio software

Microsoft Visual C++ Runtime Error
This application has requested the Runtime to terminate it in an unusual way. Please contact the application's support team for more information

this is what i get after about 5 - 7 mins of play
i first turned down mi gfx an updated all drivers
when that didnt work i went and optimised oblivion in the elder scrolls tweaking guide an it still did nothin
i havent installed any mods or software of recent to trigger this and as stated b4 it was working for several months just great.

i have done full anti virus scans and spyware ,and a defrag of HDDs (sata ll) and the registry and also disk claner and reg cleaner an im running out of options =/ plz if u kno how 2 fix a runtime error then let me kno

no the error message is

Microsoft Visual C++ Runtime Error
This application has requested the Runtime to terminate it in an unusual way. Please contact the application's support team for more information

duno wht this is but its causing me sum strife an i duno how 2 fix this