Shouldn't it be <your ui path>CMS/Admin/Default.aspx?

/Q

Thank you, that was a part of it. Now I get this: (Is it some files missing in my installation or modules/packages folder?)

Server Error in '/' Application.

The file '/UI/MasterPages/Frameworks/Framework.Master' does not exist.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. 

Exception Details: System.Web.HttpException: The file '/UI/MasterPages/Frameworks/Framework.Master' does not exist.

Source Error: 

Stack Trace: 

[HttpException (0x80004005): The file '/UI/MasterPages/Frameworks/Framework.Master' does not exist.]
   System.Web.UI.Util.CheckVirtualFileExists(VirtualPath virtualPath) +9890876
   System.Web.Compilation.BuildManager.GetVPathBuildResultInternal(VirtualPath virtualPath, Boolean noBuild, Boolean allowCrossApp, Boolean allowBuildInPrecompile, Boolean throwIfNotFound, Boolean ensureIsUpToDate) +475
   System.Web.Compilation.BuildManager.GetVPathBuildResultWithNoAssert(HttpContext context, VirtualPath virtualPath, Boolean noBuild, Boolean allowCrossApp, Boolean allowBuildInPrecompile, Boolean throwIfNotFound, Boolean ensureIsUpToDate) +103
   System.Web.UI.MasterPage.CreateMaster(TemplateControl owner, HttpContext context, VirtualPath masterPageFile, IDictionary contentTemplateCollection) +148
   System.Web.UI.Page.get_Master() +54
   System.Web.UI.Page.ApplyMasterPage() +14
   System.Web.UI.Page.PerformPreInit() +45
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +335

Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.18446

Hi,

Make sure you have file EPiServer.Cms.Shell.UI.zip in \modules\_protected\CMS. I suspect it's missing or corrupted. You can find it on \packages\EPiServer.CMS<version>\content\modules\_protected\CMS

/Q

I don't seem to have a \packages\EPIServer.CMS<version>\ folder. The closest is \packages\EPiServer.CMS.Core.<version>. I have, however, the zip in \modules\_protected\CMS, but it might be corrupted as you said.

Sorry, I accidentally deleted the UI part, it's EPiServer.CMS.UI<version>

It didn't help. Now I am wondering if 

'/UI/MasterPages/Frameworks/Framework.Master'

is the right url in epi 7.5?

I can't seem to find any indication in my folder structure that it should be.

I can find that page on other paths in the episerver installation folder, but not the one metioned above. That is if the url and folder structure is mapped 1:1.

Should EPiServer.Cms.Shell.UI.zip be unzipped?

No, CMS works fine with the zip. - and yes, it should be "/CMS/MasterPages/Frameworks/Framework.Master" instead of "UI". I guess I know your isse, you need to open the episerver.config file and change the attribute uiUrl in applicationSettings to "~/<Your path>/CMS/" instead of  "~/<Your path>/UI/" 

/Q

I solved it yesterday :) Thanks for the help! The issue was in episerver.config. I switched out the whole epi 7 site settings, with the new applicationSettings node. I think the URL was correct anyway though, not quite sure. Anyway, removing the <sites><site>... node  and adding <applicationSettings>... solved it. A lot of the things in the <sites> node are now defined in edit mode, and saved in the database, as opposed to defined in the config file.