First, check your network connectivity with the partner server. If it has gone down previously the parner relationship should be restored automatically when it comes back.
Second, you likely have a time diff issue. Standardize your time setup on ALL your physical Windows servers (NOT just on your PDC emulator. No doubt. Trust me.) (and, therefore, time is getting ready on domain clients) with the following commands:
net stop w32time
w32tm /config /syncfromflags:manual /manualpeerlist:"1.pool.ntp.org,2.pool.ntp.org,3.pool.ntp.org,time-b.nist.gov"
w32tm /config /reliable:yes
net start w32time
No need to
w32tm /resyncafter this. Time should be corrected immediately