Wireless connection to printer lost

I have a Dell XPS720 with operating system Vista that is hard-wired to a wireless modem.  Until recently the computer was connected by wireless to a Dell 948 printer.  The printer suddenly stopped working with this computer (although worked as normal with a second computer - an Acer laptop).  When I checked Device Manager, no wireless adaptors were listed.  As the user guide makes no reference to wireless functionality, I do not know if I have inadvertently disabled the device or if it has stopped working. 

I would appreciate some advice on how I can resolve this problem. 

Regards

Peter