3G Modem Interfering with Wifi?

Hi

I have been using a small wifi network at home to share what was a dialled Internet connection. Whilst I had all the usual problems with a wifi network (and still do!) another problem has reared its ugly head.

I have just got a Vodafone USB 3g modem (made by Huawei) for fast Internet access.

I am on the edge of the 3g signal put by hanging it in my office window I get access.

Since installing the Vodafone modem I have been getting problems with the wifi signal and as I type, although they are only feet from each other, my desktop and IPAQ are not seeing each others signals. Could the 3G modem be interfering with my wifi signals? I have tried different wifi adapters to no avail so I am assuming the 3G modem is causing interference??

Hope I can get help on this.
Driven to distraction
William John