Why doesn't Mac peripherals connect to wifi?

I’ve been having this intermittent issue for over 6 months and it seems that my iPad, Macbook Air, iPod Touch, and Macbook Pro do not connect to a wireless network that only a PC can connect to. I am running windows on my MBP and it connects seamlessly. On the other hand, when the MBP was operating under OS-X 10.6 there were connectivity issues. I have not done extensive troubleshooting because I am not experienced with these matters. I have researched on Apple and other forums to no avail. The connectivity is random and when it does connect, it will be operable for a couple of weeks until the following month. Information about the network: I cannot modify it when I log into it as it is being administrated by third party, and I have no control over the connectivity whatsoever. I use it as-is. What do I do to change the connectivity settings that only a Windows computer can have access to?