"fatal: reference is not a tree:" on git checkout <branch>

Hi,

Reproduce:

$ git clone https://github.com/cms-sw/cmsdist.git
$ git branch -a | grep devel-gcc48
remotes/origin/IB/CMSSW_7_0_X/devel-gcc48
$ git checkout IB/CMSSW_7_0_X/devel-gcc48
fatal: reference is not a tree: IB/CMSSW_7_0_X/devel-gcc48

It has stopped to work with the last pull request. All the references on Google 
talk about submodules, which I don't use. Any ideas what could be causing this
issue?

You can get into detached state by:
$ git checkout origin/IB/CMSSW_7_0_X/devel-gcc48 

You also can checkout a branch by doing:
$ git clone -b IB/CMSSW_7_0_X/devel-gcc48 https://github.com/cms-sw/cmsdist.git
$ git branch
* IB/CMSSW_7_0_X/devel-gcc48

Thanks,
david