Changing Document.location.hash In IE7 Overrides Event.stop(e) And Submits Form

I am writing a modification to Invision Power Board that makes replying to post via Ajax.

The "Submit" button is being overrun by Prototype's observe function. When the custom function is executed, I run Event.stop(e) to prevent the actual form from being submitted and reload the page.

I have developed and tested on Safari but users began to report bugs in IE, after investigation I discovered that the line

Code:

Is making IE execute all the code after it, and then execute its own onclick() function as if Event.stop(e) was not there. Commenting this line fixes the problem, the page is not reloaded, but this line is vital to the code.

So why do I need to set the anchor? To support the back button function after a user makes an ajax reply, pressing Back should hide the new content, and pressing Forward should make it visible. (e.g. every time the anchor is changed) This all works nicely. But not in IE.

This only happens the first time the page is visited ever, or clearing cache and visiting it again. Reloading the page fixes the problem but this is not normal behavior and users shouldn't have to reload to use the Ajax fast reply...