I really hate discovering silly problems in ArcGIS, especially as ESRI's documentation is not the easiest stuff in the world to use. Many of the solutions are things I discover by inference from the documentation. Here's this week's two:

Problem: I would like to Join a Table to a Shapefile / Layer. (Specifically, I'd like to Join a table that has tax parcel id / address / owner address records, exported from the City Assesor's database, to the County's parcel Layer.) Obviously, I right-click the Layer, and use "Joins and Relates -> Join..." I receive no error message, and the Layer has all of the fields from the Table included in it. With no data. Just blank fields.