I tried the "x" key and find it a bit misleading.
I noticed that too, and I thought that maybe there's something wrong with my old graphic card, because it's not mentioned in any review or post (except this one).
To be more specific, I found that sometimes a hotspot doesn't have an asterisk at all, sometimes there are two asterisks for one hotspot, and sometimes there's an asterisks on a hotspot-less spot...
Here is a good example from Chapter XII:

The asterisk on the left is on a hotspot-less spot, and in addition there are several hotspots in the plane area, including Amanda, that completely lack asterisks.
So is this a problem just me and BillyBob encountered, or is it like this in every version of the game on any PC configuration?