Cumming, who won a Tony Award for his work in the Broadway musical "Cabaret," was to play the Green Goblin in the long-delayed "Spider-Man" stage project, which would have reunited him with his "Titus" film director Julie Taymor.
"The 'Spider-Man' team could not resolve conflicts with my dates on 'The Good Wife' -- the CBS TV drama that shoots in New York and which I have recently joined as a series regular," Cumming explained on his Web site. "Obviously, having waited over a year for 'Spider-Man' to be green-lit, I am very disappointed that I will not have the chance to collaborate with Bono and the Edge, and to work with Julie Taymor on the stage.
I wish everyone involved the very best."
"Spider-Man" was to open in February, but its producers said it had been postponed until later in the year due to financing issues. A new opening date for the musical has not yet been announced.