First step is to see why this is happening to you. I agree it's most likely related to the configuration/local setup of the devices.
Before you reboot the device, you should navigate over to Status, System Logs, take note of the information there, try expanding it to a few thousand entries, there will be something noted in this area about what is causing your lack of internet access.
I would suggest getting a console session going, our SG-2440 Manual has a great guide on gaining access to the console.
What packages do you have installed on your device? If you run from the command prompt df -h how much disk space is there?
The more information you can get to us, the better someone can assist you.