File this under gosh darn whacky wastes of time
If you have a web service written in VB.NET which has functions which are called by ASP.NET AJAX scripts, don't ever declare the values in the function declaration as ByRef. Use ByVal instead.
ASP.NET AJAX will show a Method 500 error and you'll spend much time trying to find out why that one call doesn't work.
Again, the side effects of relearning VB.NET