RIM's real problems center around two big issues: its market is saturating, and it seems to have lost the ability to create great products. This is a classic problem that eventually faces most successful computer platforms.
A comprehensive analysis of RIM makes a good primer for the rest of us. My feeling is that RIM has tried to take a B2B product to the masses rather than build a B2C product. They've done "one size for all" instead of really understanding the new personas and their problems.
But a company's decline is rarely simple. This article examines the complexity of the issues.