I have the H50 and I have been running my i5-2500k at 1.36V with 4.5GHz overclock for about 6 months now, and it usually runs at 60-65 degrees at most. Today, it hit 95 degrees for the first time, randomly, and I had to restart my computer and undo the overclock and then wait about 15 minutes for the CPU to cooldown. It is now at around 65-75 degrees at stock speeds and voltage. What went wrong? (Should be closer to 40 right now)
More aboutsudden problems
intel speedstep disabled? are you running "fixed" voltages? if everything is normal @ theese 2 the maybe 1 pin from the heatsick came out of the hole
Re-seat the CPU/heatsink assembly using Arctic Silver 5 or similar thermal compound. What you describe is typical of a failed heatsink installation (or failed heatsink).
What Ubrales said.
You can confirm whether or not bad contact between the heatsink and CPU is the problem by touching the heatsink when the core reports 95C. If the heatsink is only lukewarm, the CPU-heatsink contact is bad and heat gets trapped in the CPU. Remove the heatsink, clean, re-apply paste, re-install.