Can't pair wireless keypad and keyboard to early 2009 MacPro.

Have OS X 10.6.8 on my 2.93 HGz Quad-Core, 460 GB electronic hard drive, 16 GB memory. Recently been having problems with my wireless keypad and keyboard. Seems they can't get thru the connection and pairing process. Have tried everything in the manuals and just won't work. Yesterday I used wired keyboard and mouse and was able to get a temporary connection and pairing. But after an hour or so they dropped out and now I can't even get a connection. When I do get a connection it will not pair. Kind at my wits ends. Can anyone shed some light on this?