Import progress bar on Windows "undefined"

While importing into CiviCRM, the progress bar says "undefined" instead of the no processing status message. The status_XXXXX file in upload directory appears to have the "No processing status reported yet" message.

C:>type status_ec19d814255a40d03336567192060796.txt
[0,"<div class='description'>  No processing status reported yet.<\/div>"]
C:>

Running under Apache 2.2 and PHP 5.2.0 on Windows XP. I'm not sure if this is related to my other problem importing data into civicrm on windows. I have a small test case that will import correctly on demo site but will fail on my local instance. I will open another issue to track that.