Jim Cramer saw some classic signs of a market bottom Thursday morning, but forced margin-selling came into play Thursday afternoon, wiping out chances for a bottom, he said on his "RealMoney" radio show .

"Too many people own too many hot stocks with margin debt," said Cramer. When that happens and stocks go down, borrowers must either send in more money to their brokers or the broker will sell the stock out from under them.

Most of the time, it's the latter that happens, he said. Forced margin selling usually begins around 2 o'clock, said Cramer, and sure enough, as the 2 o'clock hour approached, the market began to sell off.

Cramer said Thursday's action was reminiscent of what happened during the dramatic market declines of 2000, in the wake of the tech bubble. But, the difference this time, he said, is that most companies are real companies with real profits.

Thus, Cramer expects to begin seeing analysts upgrade beaten-down stocks. He also believes analysts whose estimates for oil are too low may start to raise their price targets. And, companies seeing their stock prices fall precipitously are more likely to start buying back stock.

For those who are on margin, though, said Cramer, "Get off margin right now. ... Margin is horrible."

In response to a question about Seagate Technology ( STX), Cramer said that the stock is a battleground and that there is a "lot of bad money in Seagate." It's "too hard," he said.

In response to a question about recent IPOs that are trading below their offering prices, Cramer said Avalon Pharmaceuticals ( AVRX) is "kind of interesting." Caribou Coffee ( CBOU) "doesn't have great earnings momentum," but if you buy it around $10 to $11, "you'll be OK," he said.

Cramer also mentioned Genomic Health ( GHDX) but said that "none of these jumps out at me as if you must own them," adding that "things are rough out there right now."

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