Investment firm Greenlight Capital has filed suit against Apple over a proxy proposal for its stock, reports AllThingsD. The proposal would eliminate preferred stock from Apple's charter, but in a statement, Greenlight argues that shareholders should vote against it since it wouldn't maximize their profits. "Apple is a phenomenal company filled with talented people creating iconic products that consumers around the world love," claims Greenlight's David Einhorn. "But Apple has a problem, we think. It has a cash problem."