I have a DK424 with a RPTU or BPTU (cant remember which) and today I get a call telling me: when I press 9 to get an outside line I get the dial tone and dial a couple digits of the phone number and it goes to a busy signal. When you try to call in all I get is blank air. I had them power cycle the Dk and the phones all now work fine, inbound and out. I dont have a spare BPTU so I cant swap that out with the hopes it doesnt do it again. Anybody have this problem before?