Internet connection problem on a desktop computer

There are two laptops, three mobile phones and one desktop in my household. The desktop is having WiFi connectivity issues. The signal strength varies greatly, and the signal is lost very often. All other devices connect fine. Is this a problem of my WiFi card? It is a Rail Link RT3290. If this is so, what would be a suitable substitute? Are there any compatibility issues I should be aware of when buying a new WiFi card?
