@freemangordon...
oops ! thanks a lot ... u saved my beloved n900 cpu from frying
okay, now i am using these settings and everything seems to be good till now..

# DO NOT EDIT THIS FILE - CREATE A COPY OF IT FOR CUSTOMIZATION
# minimum frequency to use
MINFREQ=125
# maximum frequency to use
MAXFREQ=850
# list of frequency configurations: each "frequency:volt,dsprate"
FREQS="0:30,90 125:30,90 250:38,180 500:48,360 550:54,400 600:60,430 720:60,480 805:60,540 850:60,600 900:60,600 950:60,600 1000:60,600 1100:72,600 1150:72,600"
SMARTREFLEX_VDD1=1
SMARTREFLEX_VDD2=1
GOVERNOR=ondemand
UP_THRESHOLD=95
SAMPLING_RATE=300000
IGNORE_NICE_LOAD=0
POWERSAVE_BIAS=0

and sr_vdd1 shows this
720:45
805:49
850:52

are these values good or i still need to reduce frequency and dsp..(p.s - no reboots till now with these settings)
thanks...