CF8 Report Builder duplicates subreport parameters

I am experiencing this problem running Report Builder under Windows XP:

1. Create a report.
2. Create a subreport that has input parameters.
3. Add the subreport to the primary report and define subreport parameters.
4. Save and close both files.
5. Reopen the primary report file.
6. Look at the list of subreport parameters for the linked subreport

I routinely find that in this scenario, any subreport parameter that I originally defined has been duplicated, such that if I started with:

varOne - #query.foo#
varTwo - #query.bar#

Upon reopening the primary report and insepcting the subreport paramaters list I will see:

varOne - #query.foo#
varTwo - #query.bar#
varOne - #query.foo#
varTwo - #query.bar#

Which causes errors when I attempt to run the report.

What's the patch schedule for report builder?