BFO85FA001

The destn arpt was unattended at night & when the plt received his last wx briefing at 0519 CDT, no current wx info was available. During arrival, the acft was vectored for an ILS rwy 24 apch & the plt was advised that current wx info was still not available. Before reaching the outer marker (faf), the plt stated (2 times) that he was not receiving the ILS localizer. However, the adf equipped acft then tracked back on course & crossed over the faf/lom beacon. At 0801, the plt was cleared for the apch & radar svc was terminated. Aprx 7 min later, he declared a missed apch, then radio & radarcontact were lost. The acft was found where it crashed about 1 mi se of the arpt at an elev of 3575'. The arpt elev was 3792'. When the local alt setting was not available & the roanoke setting was used, minimums were 630' ceiling & 2 mi visibility. The 0810 wx was in part: 100' obscured & 1/8 mi vis with fog. An investigation revealed the ILS localizer had tripped off for an unknown reason at sometime before 0755 while the arpt was unattended; it worked ok after reset.