First, we need to find what the error is. To do that, there's 1 or more things that need to be done.
In the web.config file (blog root), you'll find 1 or 2 HTTP modules for "CompressionModule". Both lines are the same and look like:
<add name="CompressionModule" type="BlogEngine.Core.Web.HttpModules.CompressionModule, BlogEngine.Core"/>
Either comment out those lines by wrapping them in <!-- ...... --> or temporarily remove the lines.
After that, try pulling up your blog, go to the Dashboard and see if you get an error again. Hopefully you'll get some meaningful error details. At this point, you shouldn't get the garbage characters anymore (the ones you had in your screenshot).
The 2nd thing you may need to do is change the <customErrors> tag in the web.config file, changing the "mode" to "Off":
<customErrors mode="Off" defaultRedirect="~/error.aspx" redirectMode="ResponseRewrite">
The error details may mean something to you so you can fix the problem. If not, please copy and paste all the error details here so we can see what they are.