Many a times I have seen that many bloggers find an error as the following:

bX-qr9qtc

ERROR:
We're sorry, but we were unable to complete your request.

When reporting this error to Blogger Support or on the Blogger Help Group, please:

* Describe what you were doing when you got this error.
* Provide the following error code and additional information.

bX-qr9qtc

Possible Reasons:

1. Generally this occurs due to a template that is not supported by Blogger's Compiler.
2. Many of you may find this error when you try to change the position of your Blogger Widgets, you drag your widgets here and there on the Page Elements Tab in Blogger Layout.
3. You sometimes think that there is a problem with the Blogger Server and think of trying it after some time, but exactly the Problem is in your Template.
4. This usually occurs because the templates from any other Blogging Platform are converted into Blogger Templates and made available to the Bloggers. It contains a lot of scripts and some conditions which are not identified by the Blogger.com's Compiler and it throws you an Error.

Solution:

For those who know HTML and CSS:

1. Try to find the code from your Blogger templates which contains scripts for Showing a Different Home Page and a Different Post Page.
   There are some Conditions in Platforms Other than Google's Blogger which contains script to show a different Home Page and a Different Post Page for example see this blog, Home Page and Post Page
   In the above given link the Home page has certain different options and the Post Page has only the post which confuses the Blogger Compiler sometimes.

OR

Go to Layout → Edit HTML and search your widget that you want to move it may look like this:
<b:widget id='Profile1' locked='false' title='About Me' type='Profile'/>
Above code is just resembling of a typical widget, Just cut this line of code from its original place and paste it wherever you want to place the widget but remember is should be in between the:
<b:section>

</b:section>

For those who are unaware of HTML and CSS:

Simply Change the Blogger Template