configuration is: DELL STUDIO 1535 CORE 2 DUO T5850 2.1Ghz 3GB 160GB
Like the previous post says, If I leave laptop on the desk, no problem about standby it resumes properly, if I carry the laptop after standy, It can not resume, I had to power it off completely by pressing power button about 2~3 secs. This makes me think that the problem is about HDD drop sensor.
I'm running Vista Home Basic Edition with preinstalled drivers and updated from Dell support site (BIOS is also updated).
This is very serious problem and Dell doesn't seem to care about it upto now.