On Wednesday, when Apple is scheduled to report its second-quarter results, the same shares opened at $122.27 — a 56% increase.

While that’s still below the price targets set by most analysts — many of whom revised their targets upward in just the past week — some think Apple’s share price has got ahead of itself.

RBC Capital’s Mike Abramsky (an Apple bear) said as much in a note to clients Tuesday. “Valuation has risen faster than peers … and while we expect near term upside around the refreshed iPhone, we continue to see elevated challenges ahead to valuation.”

Still, Apple is not in the same kind of trouble as its competitors — like Dell (DELL) for example. Apple still has rich cash holdings ($25 billion, or $29 per share), enviable profit margins (34.7% last quarter) and the deferred revenue from seven quarters of iPhone sales (which could add 30 or 40 cents to its earnings per share).

But the company has a basic problem with its fundamentals: two of its three primary engines of growth have stalled.

As Silicon Alley‘s Dan Frommer points out, the Street is expecting Apple to report that it shipped 2.1 to 2.2 million Macs in the second quarter — a year-over-year decline of 4% to 9%. That would represent the first time in five years that Mac sales have shrunk. Moreover, it’s being compared with a quarter (2008 Q2) in which Mac sales grew by more than 50%. (See chart below.)

Meanwhile, iPod shipments are also expected to shrink — a 6% decline, to about 10 million units.

The iPhone — which was supposed to fill the gap — is still on its growth curve. The Street expects Apple to report that it shipped 3.3 million units in the quarter, nearly doubling last year’s Q2 shipments of 1.7 million.

But that may not be enough to make up the difference. The consensus, according to Thomson Financial, is that Apple will report earnings of $1.09 a share on revenues of $7.94 billion — a 5.7% year-to-year increase in revenue and a 6% decline in earnings.

“How can the market justify giving Apple a 22 P/E,” asks Andy Zaky of Bullish Cross, “when it’s not growing at all?”

Zaky, a blogger-analyst who has taken his Apple profits and turned “agnostic” on the stock, acknowledges that he could be wrong. One could argue, he says, that the market has already adjusted for the current state of affairs by taking Apple’s stock price from $200 to $120. Or that Apple’s growth drivers have stalled because of weakness in the economy and not because there’s anything inherently wrong with the company.

And there are several things that could kick-start Apple’s growth. Like if the rumors are true that Apple is about to cut an iPhone deal in China, or that it’s set to unveil a new family of iPhones, or that it’s working on a new device that will be its answer to all those $400 netbooks — or that the global economy has turned a corner and started to recover.

Meanwhile, the pressure is on COO Tim Cook (standing in for Steve Jobs) and CFO Peter Oppenheimer to report Q2 results that surprise the skeptics, chart a path for growth and offer guidance for Q3 that, while dutifully conservative, reflects a little more confidence in Apple’s future.

Apple will report its earnings on Wednesday after the markets close. A conference call with reporters and analysts is scheduled for 5 p.m. ET (2 p.m. PT). Tune in here for live coverage and analysis.

See also:

• Bearish grunts from a pair of Apple bulls
• Why Apple’s shares rose as its market share shrank
• Kaufman’s Wu changes tune, ups Apple target 26%
• Barclays raises its Apple target 26%

Below the fold: more Zaky charts, including operating expenses by quarter and Mac sales by region.