Error when loading after lighthouse.

[kjels]

after i've gunned down the dropships at the lighthouse and folowed the medic to the 'secret gate' in the lighthouse. I get a error when loading to next "level".

All that happens is that there is "loading" a few seconds, and then the Menu poppes up and nothing happens.

Can anyone help me fix this problem? I do have a legal copy of hl2.Downloaded through steam.