Welcome to the PICAXE Forum.
We are sorry to hear you encountered this problem. It is not a known issue but is something we will investigate as best we can. We have tested on XP and have not seen similar issues ourselves nor had similar reported by others.
It looks like you had opened other Blockly examples before the error so it may help if you could post the Blocky program you were using when the error occurred, and describe the circumstances in which the error occurred.