Well this is going to sound very strange, but I assure you I am not joking.  If you boost a unit to equal or greater than 328,000 power or more using a unit that has had its power increased manually then the game will bug out and start automatically turning the card back and forth by itself as shown here:


This freezes this client for a few moments and fails to provide the boost.  Well that's an awfully specific problem isn't it?  Here's where it gets even weirder.  If you log-in after doing this, everyone will have disappeared:


Deleting the entire folder and re-installing it appears to do nothing.  Restarting the client or the computer, messing with anti-virus/firewall seems to do nothing as well.  Going through the other support threads I've noticed some other people have had this issue as well.