The conditions required for this failure are, or at least seam to be, very specific. What I have is a case where I have already completed research on "Medical Theory", "Soil Enhancement", and have just completed "Genetic Mapping". When the research window popped up automatically I selected Medical lab to see if I wanted to research it at this time (single left click on the green "medical lab" tab). Then I looked around at some other techs (including in other categories) and returned to the "biology" category. Then I looked at "Soil Enhancement" and got the already researched text in the lower right corner. At this point the failure became apparent. I could not select the "Medical Lab" tech from this state. Then I tried selecting other techs in this category and trying the medical lab tech again. This worked. Again I selected the soil enhancement tech and then the medical lab tech. It still would not bring up the medical lab tech from this state. Then I tried selecting techs in other categories, both those I had researched and those I had not, and returned to the biology category and selected the medical lab tech. These worked fine.
In conclusion, it looks like the medical lab tech can not be selected only after selecting the soil enhancement.
Since I have only just completed the research for genetic mapping, I am unable to state whether this failure would occur if soil enhancement had not been researched before genetic mapping was researched.
I have sent a screen shot of the research window. my prefs.ini and debug.err files to Scott.
