I'm on rackspace cloud as well and am experiencing the same problem.  I have impersonation set. The error occurs when clicking on "Browse" in the anchor popup, CuteEditor/Dialogs/SelectFile.aspx line 124

<%= CuteEditor.Impl.FileStorage.FormatSize(secset.MaxDocumentSize * 1024)%>

This is what I have in my web.config file:

<configuration>
<system.webServer>
<modules>
<add name="CuteEditor.UploadModule" type="CuteEditor.UploadModule,CuteEditor"/>
</modules>
</system.webServer>

<system.web>
<compilation debug="true"/>
  <identity impersonate="true" userName="dfw\xxxx" password="xxxx" />
</system.web>

<appSettings>
  <add key="CuteEditorTempPath" value="\\fs2-n02\stor2wc2dfw1\432221\482041\www.xxx.tld\web\content\tmp"/>
</appSettings>
</configuration>

I read in the article that the AjaxUploader needs to be used, and does the key "CuteEditorTempPath" enable it?

Thanks,

Dave.