I have the same problem and found it was caused by one of the power plant mods I plugged in. One of those wind powered plants that cost almost nothing but powered the entire city almost. That is the last time I will try and get something for nothing. Now I have deleted those plants and even taken the mod out.....but the problem remains and I have no idea how to get it back to norm...the problem is I have a huge city now with tons of hours in it..I hate like anything to have to get rid of it....but it is also very frustrating to see your funding drop in half all on its own. Any ideas would be appreciated.