Yes higher temps will cause lockups. As you overclock your cpu becomes more sensitive to high temps. For example I have a ambient temp water cooled AXIA 1.2 and it runs at 1440 and the full load temp is in the mid 80's. We have had a few hot days here in the past couple of weeks and my comp room got hot. When the cpu temp hit 95F it locked up and I had to clock it down to 1.33 in order to get it stable again. Now temps are back o normal so I cranked it back up again.
Yes I did say it will lock at 95F when overclocked. Every cpu is a little different, just like some oc better then others some can also take more heat when overclocked but in general the harder you push the more important cooling becomes.
What's so hard to understand about CPU performance thresholds. My 1G/266 will run 10.5x150 up to 30C. Then I have to drop it to 10.5x145 up to 36C. Then i have to drop it to 10x150 up to 40C and down to 10x145 above 40C. Bear in mind that at 10x150, it is right at 100W of heat ! You either get rid of the heat or suffer because of it.