As per http://forums.java.net/jive/thread.jspa?messageID=370867

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When I run NetBeans 6.8 beta using JDK 1.7.0 b75, if I enter a double-quote character, it always overwrites the current character instead of inserting.
This seems to occur in any editor window. (Java, XML)

I tested with JDK 1.6.0_16 and JDK 1.6.0_18 and it works fine with both of them.
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The subsequent posts in the forum reveal this issue affects any Swing application.