Thanks for the reply. Yes, you're right about the location not being correct on the screen shot I posted. I think at that time I was checking to see if the Layers folder was causing my problems, so I changed the path temporarily. However, the main problem seems to be with the vector data path and the geodatabase. I am able to create one dataset in the geodatabase, and then if I try to add any more, or even try to use that one dataset for any further AH analysis, the tool I am trying to use crashes (doesn't matter which AH tool).
For example: I run Sink Evaluation, which creates SinkPoly and SinkDA feature classes in the geodatabase. Then, the next tool I try to run that either uses those feature classes, or tries to create new feature classes (say, Catchment Grid Delineation, or Flow Direction with Sinks) causes the "Set Target Locations" box to pop up, blocking me from running the tool no matter where I set the locations to. I am also unable to change the path to the database in the Set Target Locations menu. It always reverts to the default (which would be fine, except the default keeps crashing my tools!).
I have reinstalled AH with the most recent version, and I have reinstalled ArcGIS. Neither has helped, so I think I will reformat my computer when I have some time. Unless you have any other ideas?:D