User Actions

[sigh71]

I'm trying to add a fairly simple user action to my project, that causes the project to fail with a given message.

here it is

<action Name="Fail Build"
DefaultProperty="Msg">

<GUI Category="Samples"
Description="Test action implemented as script"
Bitmap="User Action1.bmp">

<Tab Name="Properties">
<Field Name="Error Msg"
Type="Edit"
Description="Error Message"
DefaultValue=""
Height="36"
Required="1">
</Field>
</Tab>
</GUI>

<Build>
<Script Language="VBScript"><![CDATA[
Option Explicit
err.Description = step.Property("Error Msg")
err.Raise 1
err.Clear
]]></Script>
</Build>
</action>

the action registers, and i can add it to my project and it works exactly how i want it to....
but when i save and then reopen my project i get
"Error parsing document "C:\a.bld" is not well formed (invalid token)

and i cannot open the project file at all.
What's going on?