Today was a good day for Hughes Electronics (GMH) shareholders. But tomorrow won't necessarily be a better one.

Shares in Hughes, a stock that tracks

General Motors'

(GM) - Get General Motors Company (GM) Report

satellite businesses including the

DirecTV

home satellite service, rose 55 cents, or 2.3%, to $24.30 after

EchoStar Communications

(DISH) - Get DISH Network Corporation Class A Report

disclosed that GM was willing to listen to EchoStar's pitch to take over Hughes.

GM's decision represents a reversal of its previous stance and a complication of the negotiations for Hughes, which have dragged on for months between GM and Rupert Murdoch's

News Corp.

(NWS) - Get News Corporation Class B Report

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. Until now, GM has refused to enter into discussions with EchoStar, its competitor in the home satellite dish service, but the car company has been unable to reach a deal with News Corp., which covets DirecTV as business it can add to its satellite services in other countries.

In the

Securities and Exchange Commission

filing disclosing GM's change of heart, EchoStar warns there can be no assurance that it will be able to reach a deal with GM, or even that "substantive" discussions will take place.

The news is clearly good for Hughes shareholders, according to Mark Greenberg, portfolio manager of the

(FLISX)

Invesco Leisure Fund. "When you're trying to sell your house, it's always good to have more than one person in town who can buy it," he says.

And EchoStar, which is raising $1 billion through the sale of convertible notes, appears to have enough money for a down payment. The bond sale "shows they're serious about it," Greenberg says. "It shows they can raise more money, too." (Greenberg's fund holds shares in Hughes, EchoStar and News Corp., as well as in

Pegasus Communications

(PGTV)

, which markets the DirecTV service in rural areas.)

But one portfolio manager, saying that money wasn't the biggest problem facing an EchoStar bid, says he sold all of his Hughes holdings today. Speaking on condition of anonymity, the manager says, "I'm not as worried about money as I am about the regulatory issues." The antitrust issues raised by the combination of DirecTV and EchoStar, the two largest direct broadcast satellite providers in the U.S., could delay the merger up to two years, the manager says.

Meanwhile, the manager says he doesn't think Murdoch will try to beat any offer to be made by EchoStar Chairman Charlie Ergen. "I don't think Rupert will pay up," the buysider says. "I think they've put their best offer forward after nine months of negotiations. I think they'll let Ergen win this one." The manager says it's the expectation that Murdoch will try to outbid EchoStar for Hughes that sent News Corp. stock down 70 cents, or 1.9%, to $36.53 Thursday; he added to his position in News Corp. Thursday on the expectation it won't.