wifi turning off on its own

[Marin85]

Hi,
I´ve been recently experiencing the following problem: after some intensive work using my WiFi (IE7 browsing, ICQ, Skype, Office Outlook as well as sometimes Windows update and uTorrent) the WiFi light indicator turns off and my internet connection is broken for a few minutes (always different). The system can still recongnize any available wireless networks except for the one I was connected to. The same occurs with or without AC installed and also in different networks (with different routers). Now I´m using Vista Business 32bit, but it has also happened under XP. This problem seems to appear when my TP, respectevely the WiFi has been on for several hours.
Is this a symptom for a problem with my WiFi adapter or is it just normal for the Intel (R) PRO/Wireless 3945 ABG Network Adapter?

Thanks in advance and Happy New Year!

Marin