Internet Connection Drops Out after 5-20min. PLEASE HELP!!!

I have 2 laptop computers that use wireless connection to the Internet. One of them is eMachine (one year old) M6805 series and that one WORKS all the time perfectly. The other one is brand new Toshiba L25-S119 and this one have some connectivity problems. I used both laptops at the same location at home where signal strenght is excellent. (Both use Windows XP). The Toshiba (depends on its mood) works fine for 5-20 minuts and then drops connection, but it not a rule. Sometimes it stays connected all the time and does not disconnect. When it does disconnect from Internet I have to reboot the machine and then I am able to surf the Net again...but never sure for how long. What could be a problem here? Thank you so much for your time to read my message and any potential help. Jan