There have been at least two bugs in the ColdFusion MX Administrator's ability to properly update the JVM settings in cf_root/runtime/bin/jvm.config when using the Java/JVM page to enact the change. A technote was just released for How to upgrade the JVM shipped with ColdFusion, which demonstrates how to change JVM settings from the Administrator. I recommend that you familiarize yourself with the contents of the jvm.config file and carefully edit the file by hand instead, after making an original back up copy.

In ColdFusion MX 6.1 (fixed in Updater 1 for 6.1) when using the CFAdmin to edit the Java/JVM page, the -server java.args list item is incorrectly moved from the first position to some other position. The -server switch must be in the first position when present, otherwise ColdFusion won't start and the error Unrecognized option: -server will be reported.

In ColdFusion MX 7.01 (not fixed as of CHF2) edits made via the CFAdmin incorrectly modify the values of the -Dcoldfusion.classPath argument to java.args. Paths within that argument have the "../" incorrectly removed from them.

For example, this correct option:

view plain print about

will be incorrectly changed to this, which lacks the "../" part:
view plain print about

The result is that the ColdFusion server will not start, HTTP 500 errors will return for page requests, and the logs show that none of servlets that define the ColdFusion server itself are loading.

An example of the main CFMSERVLET not loading follows:
view plain print about
104/04 09:56:21 user failed to load: coldfusion.CfmServlet
204/04 09:56:21 error
4at coldfusion.bootstrap.BootstrapClassLoader.loadClass
5 (
6at java.lang.ClassLoader.loadClass(Unknown Source)
7at ...