The images for the techs is in \Program Files (x86)\Steam\SteamApps\common\TerraTech Beta directory. How many saved techs/images do you have? I'd try moving them to another directory and trying just one to see if maybe one of the images is corrupt somehow. Just be sure to save them off to another directly and not delete them.
I just cleaned out my list of techs because it had gotten too long over time and none of the saves were useful anymore.
I had a similar event happen in 05.19 in the R&D with a tech I had built in 05.12, and was wanting a couple of the large pad silos(had gon back to the 5.12 to build it as 05.19 only lets me build for about an hour then OOM crash amd it took two hours in 05.12 to build the tech