Eclipse plugin throwing an error when attempting to load Java code coverage

We are using TeamCity 6.5 and Eclipse Helios SR2 for our Java development.  I have a build configuration that collects code coverage data using the IDEA coverage engine. This seems to work great, however I cannot load the coverage data using the Eclipse plugin.  From Eclipse, I select the menu TeamCity -> Code Coverage Data, then I select the build configuration, then hit OK.  After that an error window pops up that says:

"Loading TeamCity Coverage Data" has encountered a problem:

For input string:
"my/company/package/MyJavaFile"

Clicking on the "Details" of the error dialog yields the exact same "For input string" message.  Any ideas what would cause this error? Is there a log I should look at?

-Mike D.