Darkforest Group FW Network
Have you tried reflashing? If it still reboots after reflash, flash another FW(e.g. xeja1) and test again. Maybe something went wrong with the first flash or it could be a FW problem or your Jet could be defective.
You're able to clear the cookies and such? When does this error occur? When you try to enter an URL? When you enter the home page?
This is really strange. Maybe you've messed around with some of the internals menu settings?
Are you using gprs/edge/hsdpa or wifi? Have you set all the connection profiles? Can you access to internet via opera mini or some other browser than Jets own? Maybe you should take it to a service center and forget to mention about your own flashing experiences