This is a known bug in the Android browser - it is very annoying. Your only option is to use a blur radius of 1px or higher.
Check out the bug report at http://code.google.com/p/android/issues/detail?id=7531
One commenter said they circumvented it using 0.1f as the value - this did not work for me the last time I tried - only 1px or higher worked.
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