Lots of BizTalk Compiler Errors

So I chased my tail for an hour or so trying to get to the bottom of this problem. All of a sudden, I was getting tons of compiler errors in my orchestrations project. For example, it was asking me if I was missing assembly references because it could not find a variable that was defined in the same orchestration! Weird stuff like that. And no exclamation points on my shapes, no red squiggly lines anywhere. Nothing to tip me off as to what was the problem with the error.

I finally found the following forum post that put me on the right track: http://209.8.76.204:82/BizTalk_Orchestration/rn-207960_My_Biztalk_Compilerquot;s_Gone_Mental_!!.aspx

Turns out I had commented out the following lines in an expression shape:

//currFileLocation = currFileLocation.Replace(@"\\", @"\");
//currFileLocation = currFileLocation.Replace("//", "/");

I have comments all over the place in my expression shapes, but when these lines were commented was when I started getting all those errors. For some reason the compiler was not completely ignoring these lines, although it appears the designer was ignoring them. After deleting the lines, the project built without any problems.

Failed to load source schema when opening BizTalk map

A unit test project in my BizTalk solution caused some problems. When I tried to open certain maps to view them, I would get an error stating the map could not load the source schema, and asking me to select a new schema to replace it. When I clicked yes, I received an error stating Failed to load the source schema, and then no mapper would open up. I was completely unable to view these maps in the designer until I removed the unit test project from my solution.