After killing one of the three choices for the Dark Brotherhood entry quest, you cannot fast travel nor even bring up the option to set your marker on any major holds in Skyrim. Although places you have not visited yet will allow you to place your marker.

This has happened 100 percent of the time as I've gone through it, not a major bug but this morning I only had an hour to play (work svcks!) and tried to fast travel but as it ended I didn't even manage to see the sanctuary. No big deal but I wanted to know, has anyone else had this issue on PS3/PC?

The issue is resolved when you discover a new location and enter/leave then you can fast travel again. As it stands this is by no means game breaking haha, but for those of us who use fast travel occasionally to get the most out of short lived Skyrim experiences, it's a little disheartening, and likely resolved very quickly.