Please help.

I cannot open my minecraft world.  A few seconds after I click on it, it says "The software was closed because an error occurred."  I have looked all over the web trying to find a solution to this, but cannot find one.  It seems many people have had the same issue.  Mine started today, but many others started in the last few weeks.  The only resolved postings on Mojang are solved because they refer to another post with same issue, but those other posts are unresolved.

My daughter has put countless hours into creating this minecraft world and would be really upset to lose it.  Probably never play minecraft again for fear of it happening again.

She has several other worlds created before and after this one that still open, although these she has spent little time on and doesn't really care about.