It could also happen if network drives on servers that don't exist are being referenced somewhere, since there's a 30 second timeout on them (set by Windows, not Opus).
You can use Process Monitor to see which files/folders are being accessed while the delay happens, which usually points to what's going on:
You can also make some process snapshots while the delay is happening and send them to us if you want us to see if those indicate what's happening: