One tire getting hot?

[Knanthrup]

Strange situation, but it appears that I have one tire (drivers side front) that gets very warm after driving. However, the wheel itself does NOT get hot. Also, the passenger side front is still cool. I'm trying to figure out if this is a symptom of a problem... here's why

I actually had that same side tire go completely flat while driving on the freeway. Granted, the tire had many miles and years on it, but it still 'appeared' to be in good physical condition. I could not find any cause for the flat which really bothered me. It was not a slow leak, it went flat very quickly, but didn't appear to "blow out" or at least I didn't hear anything. The tire was VERY hot when I pulled off and felt it.

So I got a new tire to replace that one and now that one is feeling very warm as well. I should really replace the other front tire so they match perfectly, but I'm not sure if a slight mismatch in tires would cause this. If there is a problem, I REALLY don't want the new tire to blow out or go flat like the last one did. Not sure if an alignment could cause this - didn't notice any abnormal wear on the old tires?