I have seen a few posts with problems selecting silhouette edges but none seemed to have any solution.

Problem: when selecting silhouette edges in a sketch (for dimensioning, converting an entity, etc) the edges will sometimes be selectable and other times not even get highlighted as if they didn't exist. The silhouette edges seem to only be selectable once.

Solution: The only solution so far is to exit the sketch (sometimes causing problems since the sketch was not ready for an extruded cut for example) and re-enter the sketch. Then the silhouette edge can be selected and converted to an entity so you don't "lose" it again. Using the selection filters does not solve the problem.

I am running SolidWorks Premium 2011 x64 SP3 on Windows 7 Professional SP1 on a 64-bit system. If anyone has a better workaround or confirmation that this is in fact a bug, I'd be interested to know since it is becoming quite frustrating.