My Dell E2210H LCD monitor was really wonky.
Powering up from sleep, it would only occasionally come back to life, usually after resetting itself several times.
More often, it would power off or go into power saving mode, leaving the front panel buttons inoperative.
Occasionally it would reset or power off while operating normally.
Here's how I fixed it, using my DIY ESR test harness to find a bad capacitor without desoldering.