macmini 1.5 Solo & Linksys WAG354G Router

Hello. I have recently purchased a Mac Mini 1.5 Intel Solo. I already have a Windows Laptop which is connected to the the router via cable. My router is a Linksys WAG354G (WiFi enabled). I have been trying to connect the Mac Mini to the wireless network (Linksys) but all I get is the "cant connect to specified network message). The reception meter on the macmini keeps boumcing up and down and it sees the network and then it does not. My wifi reception is reasonable (not perfect, but tested with my laptop). Are there any compatibility issues? I have tried almost everything. Interference robustness, 802.11b and g mode and mixed mode. Even changed the channel from 11 to 13. I must note that the problem is only when I use AirPort (wifi) not via cable (tested). I have no problems with security so I even disabled the security and have the Wifi network free. Please tell me what to do because it is driving me crazy.

I would like to mention that the mini HAS connected to the wireless network ONCE successfully (G mode, channel 13) but at a somewhat low speed. Since then nothing. It happened after days of settings changing and updates.