An odd and unusual glitch

[Zarkon]

I was playing as LA Ermor, which is a great deal of fun, and after a couple hundred turns the game became corrupted. Most of the game still runs fine, but I've noticed a couple of odd problems.

Double clicking (to select all units of type) has no effect.

Keyboard commands (such as 'e' to select all units of two or more experience) do not work.

I started a new game & none of these problems occur. Is this sort of thing common with massive numbers of units? As LA Ermor playing against the AI I was able to build up thousand unit armies.