unable to install cuda 5.5 on ubuntu 12.04

I downloaded the newest Cuda Release from the nvidia developer web site to my ubuntu workstation. If I try to install cuda-repo-ubuntu1204_5.5-0_amd64.deb I get an installation GPG NO_PUBKEY error.
I already tried
apt-key adv --recv-keys --keyserver keyserver.ubuntu.com D88C3D385C37D3BE
and to download the release key directly from
which seems to be the wrong address.
Do you have any hint for me how I get around this error?
Thank you very much!

Just to make sure, if you run apt-key list, does it show a “cudatools” entry?

The URL for the public key file is:

The cuda-repo-*.deb packages are supposed to take care of this, but perhaps you’re behind a firewall, or some other network issue is blocking the access of the file.

To recreate what the package attempts, run:
wget -q -O - http://developer.download.nvidia.com/compute/cuda/repos/GPGKEY | apt-key add -

Alternatively, if you download the file separately (perhaps to move around a firewall), you can do this:
cat GPGKEY | apt-key add -