Yeah, I use quotes a lot because otherwise I find the results are pretty poor (ie. they seem to be more likely to miss at least one of the terms I searched for, and if I'm searching for a phrase then an unquoted phrase could have its words scattered all over the place rather than be treated as a phrase).
This was in fact an issue with queries containing quotes on our /lite and /html sites. It should be fixed now. Let me know if you see any other issues.
What happened is we frequently get hit by bots trying to scrape the links from our /lite and /html sites and we have to react by creating rules to try to block them. This particular rule, was over-aggressive. Our ops team is going to discuss internally how to prevent something like this from happening again.