If you publish a SharePoint blog through UAG, you will not able to using a blog writer (such as Word or Live Writer).
The action shown in this poste were done using Live Writer.
When you try to post to the blog published through UAG, you will have an error during the uploading process.
Same type of error will occur when you will try to configure (or update) your blog writer.
To solve this issue, you must configure your UAG trunk to disable scripting.
Open the Trunk configuration.
Go to the Session tab and enable the option Disable scripting for portal applications.
Once the configuration has been saved and applied, you will be able to post using your blog writer.