PLT OF AN SMT TWIN FAILED TO OBTAIN LNDG CLRNC AFTER AN INST APCH IN IMC CONDITIONS.

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FLYING IFR W AT 16000 FT AND PICKING UP A LITTLE RIME ICE OVER THE ROCKIES; I TOLD ATC MY CONDITIONS AND ASKED FOR LOWER AND THEY GAVE ME 14000 FT; THIS HELPED A LITTLE; I WAS GOING INTO OGDEN FOR FUEL. ATC GOT ME DOWN IN THE FLAT LAND; AND VECTORED ME LOWER FOR THE ILS APCH INTO OGDEN. I ENCOUNTERED LIGHT RAIN AND FOG. ON THE FIRST APCH I WENT THROUGH THE LOC AND ATC VECTORED ME AROUND FOR ANOTHER APCH. WHEN THEY CLRED ME AND TOLD ME TO CONTACT THE TWR; I THOUGHT I SWITCHED TO MY OTHER RADIO; AND TOLD TWR I WAS INBOUND. I HEARD NOTHING. THIS COULD HAVE BEEN ICE ON THE ANTENNA. AFTER LNDG AND TURNING OFF RWY I CONTACTED GND AND SHE SAID I WAS NOT CLRED TO LAND. I WAS TOLD TO CALL TWR CHIEF. WHILE TALKING TO HIM HE SAID THERE WAS ANOTHER ACFT TAKING OFF ON A XING RWY. I ASKED HIM IF THEY KNEW WHERE I WAS ON THE APCH AND THEY HAD ME ON THEIR RADAR AND HE SAID YES THEY KNEW WHERE I WAS ON THE APCH ON THEIR MONITOR; IF SO WHY DID THEY RELEASE THE OTHER ACFT FOR TKOF. I JUST DO NOT UNDERSTAND THE TWR OPERATOR'S THINKING WHEN IT COMES TO MAKING SURE ACFT UNDER THEIR CTL REMAIN SEPARATED.