Shares of Garmin ( GRMN) plunged Wednesday after the stock was downgraded by a Wall Street firm over fears of competition-induced price pressures and slowing growth for personal navigation devices in Europe.

The stock was recently off $9.38, or 11.7%, to $70.85. The drop brings Garmin's stock down by more than one-third in just one month.

Deutsche Securities analyst Jonathan Goldberg downgraded the stock to a hold from buy and reduced his price target to $90 from $125.

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"While we think the near-term still looks good, the increasing uncertainty for 2008 means that Garmin can no longer attract a premium multiple, especially in light of the recent market sell-off," wrote Goldberg. Deutsche Securities owns shares of Garmin and makes a market in the stock.

Garmin's fall from grace started with concerns about increased competition in the navigation device market, especially from rival TomTom after that company bested Garmin in its bid to buy Dutch mapping supplier, Tele Atlas.

"TomTom management came across as being more aggressive about their plans in the US this year, causing us to question the pricing discipline displayed so far," Goldberg wrote.

Analysts also have been less than pleased with Garmin Chief Financial Officer Kevin Rauckman's recent comments that pricing is expected to fall and margins will be under pressure.

While Rauckman believes the increase in volume could make up for the decline in margin, it hasn't alleviated analysts' concerns. "In our conversations with Garmin, we sense the first notes of caution," wrote Goldberg.

However, some money managers are holding the bullish line.

The company is likely to report a strong fourth quarter and despite fears of pricing pressure, at its current levels, the selloff may be overdone, says Joe Biondo Jr., chief investment officer for Biondo Investment Advisors, which holds Garmin in its portfolio.

"Clearly any pricing pressure will affect the company's valuation," says Biondo, "but at this point if margins hold up and customer adoption trends hold up for the next year or two, then the stock is pretty cheap."