We've done two bits of work this week. Replacing our edge switches (old 3Com 100Mb switches to new HP Gb switches) and (Windows) updating all our servers.
Since yesterday I've noticed that DHCP is behaving peculiarly. When running a Ghost session yesterday all the clients had APIPA addresses. IPCONFIG /RENEW got a correct address. Again today I've spotted some PCs with APIPA addresses, yet other PCs are fine (perhaps because they were left long enough to get an address).
There are a couple of errors on the DHCP server (Win 2012) re. contacting Active Directory, but there are one or two of those dating back to November as well.
Any ideas where to start trying to troubleshoot this? Could a Windows Update have triggered this? Could it be our new edge switches? (I've logged this issue with the consultant that installed the switches)