iMac Wireless Internet Connection Issues

[milky bar kid]

Hi all,

Past week or so my wireless has been playing up, all other devices on my network are working absolutely fine, e.g. Windows PC's, iPhone, Xbox 360. Sometimes I just can't see my network at all but most of the time I can see it and connect but just cannot access the Internet. The weird thing is, even though I'm connected I can't even access my router settings. A wired ethernet connection will work normally and a temporary fix seems to be to log into a guest account which connects, then when I log back into my account everything seems fine for a couple of days. This would lead me to believe it is a software related issue? Any help appreciated as its becoming a little frustrating.

Thanks

 

[MTShipp]

Before packing up my iMac for shipment back to Apple (freezing), I watched some more HD video trailers. Their sizes were from 140-250MB. Though on an 'N' connection, it was painfully slow. I mean I was having to pause Quicktime for 3-5 minutes so enough would download to begin playing. My Extreme is connected to a 10MBit cable connection. Even my old Dell wireless laptop was pulling faster at G speed!