Auto-update includes the -nocache flag as part of it's HTTP GET request of both map.xml and version.xml files. This is an unnecessary flag, because of the fix for 6478142 & 6656032.
It is believed the original thought behind the -nocache was to ensure the client was always getting the latest XML files, however the cache time can be specified on the server side. Allowing a cache would prevent subsequent calls to the Sun server for XML files that were already downloaded earlier in the same update check. (we currently download map.xml twice, and version.xml 2-3 times)