Unable to add CU13 patch to my 2008 R2 SP1 server

I need a specific version of SQL for an app I'm using.  So I patched my 2008 R2 SQL to SP1.

This seemed to put me at 10.50.2500.0

Then I installed CU13.  The update seemed to go, but my server rebooted and continued to update.  It stuck for half a day at "Applying update 26 of 39....."

I was forced to reboot.

Now I cannot add CU13 - I'm still at 10.50.2500.0 and when I run CU13 it passed all checks, then when I go to update, it says:

"There are validation errors on this page.  CLick OK to close this dialog box.  Review errors at the bottom of the setup page, then provide valid parameters or click Help for more information"

At the bottom it says;

"There are no SQL Server instances or shared features that can be updated on this computer".

I then checked my application (SCCM) to see if it thought the server met the requirements anyway.  No, it still complains (it needs at least CU6).

What should I do now, since it seems it's half way installed or something?

Thanks