Error: File Manager is currently unavailable.
DotNetNuke.Services.Exceptions.ModuleLoadException: C:\intranet\Admin\Files\FileManager.ascx.vb(780): error BC30560: 'ZipEntry' is ambiguous in the namespace 'ICSharpCode.SharpZipLib.Zip'. ---> System.Web.HttpCompileException: C:\intranet\Admin\Files\FileManager.ascx.vb(780): error BC30560: 'ZipEntry' is ambiguous in the namespace 'ICSharpCode.SharpZipLib.Zip'. at System.Web.Compilation.BuildManager.CompileWebFile(VirtualPath virtualPath) at System.Web.Compilation.BuildManager.GetVPathBuildResultInternal(VirtualPath virtualPath, Boolean noBuild, Boolean allowCrossApp, Boolean allowBuildInPrecompile) at System.Web.Compilation.BuildManager.GetVPathBuildResultWithNoAssert(HttpContext context, VirtualPath virtualPath, Boolean noBuild, Boolean allowCrossApp, Boolean allowBuildInPrecompile) at System.Web.UI.TemplateControl.LoadControl(VirtualPath virtualPath) at System.Web.UI.TemplateControl.LoadControl(String virtualPath) at DotNetNuke.UI.Skins.Skin.InjectModule(Control objPane, ModuleInfo objModule, PortalSettings PortalSettings) --- End of inner exception stack trace ---

What a nasty message to receive within your portal as your trying to upgrade to a new version of the software.

I searched the Internet and found a few articles that explained a few things.  In my particular case I simply had to delete the ICSharpCode.SharpZipLib.dll file in the bin folder.  This allowed me access back to the file manager.

Hope this helps some people with the issue.