I am getting this same problem.
I am able to run the application fine in my local WebSphere 6 environment. In my stage environment I am getting the "No default implementation found" error when attempting to login.
I am guessing that the libraries between the two environments are different. I will let you know if I find anything.
I got the solution. This is what I did.
These errors are caused by a classloading conflict involving different versions of the Xalan XSLT processor classes shipped with ColdFusion MX 7.0.2 and Websphere 5.1.1.
To resolve these errors, stop your Websphere server, remove xalan.jar from the /cfusion.war/WEB-INF/cfusion/lib directory and restart your Websphere server. This will cause ColdFusion to use the Xalan classes included in the /WebSphere/java/jre/lib/xml.jar directory.
I attempted these instructions and I am still receiving the error message. I am having a difficult time see any sort of server logging from this error. I am also running WebSphere 6. Any other ideas or conflicting jar files?