Leader can't rush?

[Geofflightning]

I've had a couple great leaders, at least one from military, and I think one for science, that were not able to rush things all the time. Sometimes the situation can be remedied by finishing and starting a clean slate of shields on a new project, other times, I had to change it to regular improvements. Is there a way to tell when this will happen?

 

[Turner]

MGLs cannot rush Great Wonders. They can rush Improvements (Useful for Palaces) and Small Wonders (useful for Forbidden Palace, etc.).

Might be best to post a save of when you couldn't rush what you were trying to. We could give a better answer then. AFAIK, there are no restrictions (aside from above) on rushing.

 

[wilbill]

Sometimes the situation can be remedied by finishing and starting a clean slate of shields on a new project, other times, I had to change it to regular improvements. Is there a way to tell when this will happen?

Sounds like you had "tainted" shields -- from forest chopping or disbanding a unit -- in that city. You can't build Great Wonders with those shields.