It looks like the national credit crunch is starting to hit Silicon Valley start-ups. We’ve heard that venture-backed companies with Comerica money market accounts have had their accounts frozen, and when we asked Comerica spokesperson Sara Snyder about it, she didn’t deny the rumors.

Snyder didn’t explicitly confirm anything either, but pointed to this New York Times article about problems in the auction-rate note market and said, “At Comerica, we are working with customers on a case-by-case basis to assist them with their liquidity needs.”

Venture Wire is also reporting that an informal survey found that 20 percent of 60 venture-backed start-ups in an informal survey have money in auction-rate notes.