We noticed that a recent security vulnerability in Internet Explorer VML has led some users and organizations to disable VML entirely. This disables polylines for Internet Explorer users of the Google Maps API. We expect to release a fix this week.
We strongly encourage all API page authors to double-check that they are following our guidelines regarding VML, which may be necessary for us to workaround the VML issue. Specifically, the following CSS style rule should be included on all pages that use polylines: