Here we go.... from
Fox 6 Milwaukee News:
"(Milwaukee, September 18, 2006) You might still have a couple of questions about E. coli. Here are a couple tips to keep in mind in the kitchen. Avoid all fresh spinach-- bagged or not. Canned spinach is safe-- because it's heat-treated before the canning process. Frozen spinach isn't... be on the safe side and toss it out. You might think washing the spinach or cooking it will get rid of bacteria. It will-- but not all of it. The FDA is still looking for any other possible source of E. coli. that means you should take extra care washing and cooking your. "
I think they had said that there's a 1% chance that cooking the frozen stuff could still leave some e.coli in there (but don't quote me on that)...
Personally I wouldn't risk it. I'd just stay away from ALL spinach until this has all been resolved.