Mailto limit fixed in R8, but now gives strange message in R7

Forever, there’s been a problem with Notes having a limit of about 250 characters in a mailto: url - all other characters would be dropped. I thought I had found a fix to this in R7 by changing the syntax to mailto:?subject=?body= (instead of the expected ?subject=&body=). Unless I am totally insane or was having a serious delusion, this worked in many tests.

Now I have installed R8 on a machine in a new directory, so that I have both available. Now mailto works without limit in R8, but no longer works in R7. Instead of truncating characters, it gives a pop-up box error saying “File does not exist”. I suspect this has something to do with a registry setting, but don’t know where to look besides mailto/shell/open/command in HK_KEY_LocalMachine and HK_Classes_Root both of which seem OK.

Does anyone have an idea?