OTTAWA — Research In Motion said on Friday that its previously unwanted BlackBerry PlayBook tablet was finally selling. But the steep discounts that prompted consumer interest in the device have forced the company to restate its earnings expectations.

A $485 million writedown for the discounting, along with costs related to a worldwide shutdown of BlackBerry service in October, caused RIM to warn that third-quarter revenue would be “slightly lower” than the $5.3 billion to $5.6 billion it had previously forecast.

In a statement, the company also said that it did not expect to meet its earnings target for the year. RIM will announce official results for the third quarter on Dec. 15.

RIM has repeatedly struggled to meet targets this year as it worked to stem a loss of market share for BlackBerry phones in North America. Friday’s restatement sent RIM’s shares down by $1.81, or 10 percent, to $16.77 a share, on Nasdaq.