The roller-coaster ride continues for investors in

Research In Motion

(RIMM)

.

The wireless company's stock fell nearly 12% on Friday to $77.75. The drop was the third big swing in three days for RIM shares.

Analysts chalked up the latest decline to rumors that a decision is imminent in a long-running patent suit against the company. The suit, currently at the appeals court level, could force Waterloo, Ontario-based RIM to pay substantial royalties in the U.S. or possibly shut down its services in the country entirely.

The rumor is "a believable story," said Rob Sanderson, who covers the company for American Technology Research. "It makes people nervous." (Sanderson does not own RIM shares and American Technology Research does not do investment banking.)

NTP, a Virginia-based holding company that owns patents related to wireless technology, sued RIM more than two years ago. Last year, a federal court awarded NTP $54 million in damages. RIM appealed the ruling, but continues to recognize costs related to the judgment and the case.

RIM declined to comment on the speculation about an impending decision in the court case. The Court of Appeals for the Federal Circuit, which heard the appeal, has no timeline for a decision, a court representative said.

The potential for a legal setback comes as RIM's shares have been trading at a pricey multiple following a huge run-up in the stock price. Even after Friday's decline, RIM's shares are up more than 130% on the year, and the company is now valued at about 80 times its earnings over the past 12 months.

The legal setback rumor followed

reports earlier this week about customer dissatisfaction with RIM's

new 7100 series of smartphones. Citing interviews with customers and mobile-phone stores, a couple of financial analysts reported that T-mobile, which distributes the 7100t in the U.S., has seen high return rates and high technical support costs for the phone.

Those reports helped send RIM's shares down 10% on Wednesday and another 5% in early trading on Thursday. The company's stock ended the day Thursday up more than 4% after other analysts suggested the concerns about the 7100 were overblown.

For its part, T-mobile, which is owned by

Deutsche Telekom

(DT) - Get Report

, said in a statement on Thursday that reports of high return rates are "not accurate." Meanwhile, the customer support costs for the phone are "on par" with that of other smartphone-type devices.

In addition to voice services, smartphones typically offer access to the Internet and data networks, calendar and address book features.