Unfortunately I see this alot.
Different brands don’t like to play well together. (What about standards right?!?)
Also, WEP and WPA/WPA2-Personal are completely and inherently different.
A WEP cannot authorize a WPA/WAP2, and iut can’t happen VICE versa either…different security algorithms. So if you can get them both on the same page (and I suggest the more secure WPA2) then your problem will probably go away.
Hope this helps!