Anyone else have this issue with Pro Paste: The resin has become dried out, crystallized, lumpy...less so in the middle.

The hardner is just fine, no issues.

No, must be old.  Try nuking it for a few seconds in the microwave.  That works for liquid epoxy.  Do it in stages, so not to overcook it.

My rod bond does that on occasion.  Like Mick said, a couple 5 second blasts in the microwave will fix it like new.  

Crystallization of epoxy resin is not any indication of being bad or old. Solid form is its natural state. Usually, its fluctuating temperatures thats a catalyst for crystallization.

Simple heat treatment mentioned above will remedy crystallization. A more controlled temperature of about 50°C will make sure you dont over cook it or damage any additional properties it may have (especially the paste resin).

A safer way is boil a cup of water and put the container in the cup.