From the Mercury Support Site:

This patch is highly recommended for users of QuickTest Professional and Astra QuickTest version 5.5 running tests in conjunction with TestDirector version 7.x. Installing this patch will fix a problem with the overwriting of existing test results when the test is run from TestDirector. The patch, which is named "QTP5.5P26" can be downloaded from the "Download Patches" link on the CSO web site under "Astra QuickTest -> 5.5".

"They were painters and they were painting themselves a lovely world.."