Now it happened again: D&D stopped working. It seems, indeed, that some application causes some conflict. I suspect Kaspersky Antivirus, ABBYY Lingvo, PowerPro, Sysinternals Process Explorer, because after I exited EE and these 4 applications, and restarted EE, D&D worked fine again (even after I started those 4 applications again). Next time I’ll do it step-by-step to determine which one causes the problem.