1.4a1: need help identify an error

Hello,
I'm trying out 1.4a1 on my application.
Something breaks from 1.3.2 and firebug returns this error message:
name is undefined
jquery-1.4a1.js
Line 4047
which line is:
name = name.replace( rupper, "-$1" ).toLowerCase();
Can you help me see if this is due to an intended non-backward
compatible change, or should i file a bug? What could this be related
to?
Many thanks,
Alexandre
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