Hiya. Not sure if you're still having the issue (since you started this thread a month and a half ago and all) but, regardless, I do have a possible solution for this.
WoW UI Designer uses the Application.Settings element available in the .NET Framework and, thus, doesn't save the settings in the program directory or the registry. Uninstalling the application will not clear out the configuration files, so the "load addons" setting persists even if you try reinstalling the application.
The exact location of the settings file varies slightly depending on which OS you're using. If you are using Windows XP, it'll be in this directory:
Code:
<system drive>:\Documents and Settings\<username>\Application Data\SSC\wowuides.exe_Url_wscuaug3diqt1blkpy4bwrc4go4bbusb\1.0.300.0
...and if you're using Vista or Windows 7, it'll be in this directory:
Code:
<system drive>:\Users\<username>\AppData\Local\SSC\wowuides.exe_Url_wscuaug3diqt1blkpy4bwrc4go4bbusb\1.0.300.0
There are two ways that you can go about fixing the issue. The first, and easiest, method is to simply delete (or rename) the user.config file. WoW UI will recreate it when you start the program, but you will lose your custom settings.
The second option is to open the user.config file in a text editor. Look for the following lines (it should be lines 32-34):
Code:
<setting name="LoadAddons" serializeAs="String">
<value>True</value>
</setting>
Just change the value to "False" and you should be a-okay. Depending on where WoW UI Designer is crashing, you may have to disable the LoadFrameXml setting as well. It should be right above the LoadAddons setting.
Hope this helps!