Seattle-based lender HomeStreet today became the latest company to postpone its IPO due to market volatility. It was the third company to do so today, following 3D motion sensor maker InvenSense and Portuguese mobile payment company TIM. Two others — — postponed their offerings yesterday.

That means that five of this week’s dozen expected offerings are already on ice, with expectations that more will kick the can shortly. In fact, it wouldn’t be surprising if none of them get out (despite this afternoon’s late-market surge).

But if you’re looking for a dark horse, put your money on Carbonite, a Boston-based provider of online backup solutions for individuals and small and mid-sized businesses. The company is looking to sell 6.25 million common shares at between $15 and $17, which would give it an initial market cap of $384 million if it prices in the middle. A source familiar with the offering puts its chances of pricing this week at around 70%, so long as we don’t experience another major swoon like yesterday’s. Key is the company’s 82% renewal rate, which reflects a visible pipeline that could soothe nervous investors.

Beyond that, the IPO market really is waiting for big-name issuers like Groupon and Zynga to price after Labor Day. That’s when we’ll know if these postponements are just a blip, or an indication that the IPO window has begun to slam shut.