As if they weren't already upset about the growing bad-mouthing of what critic Roger Ebert calls "IMAX Lite" screens being installed in multiplexes, IMAX investors learned Tuesday that the movie most had expected to become the biggest hit of the year won't be available on IMAX screens until two weeks after it begins playing in conventional theaters. According to the Hollywood Reporter , Harry Potter and the Half-Blood Prince , which opens theatrically on July 14, won't begin showing in IMAX theaters until July 29 because IMAX has a month-long agreement with Paramount to screen Transformers Revenge of the Fallen. Shares of IMAX have fallen nearly 6 percent on word of the Potter delay.