Dir Function - Invalid Procedure Call Or Argument

When I step-through my code below, it always opens the first file in the directory "C:Pyramid Files", but when it comes back to the Pyramid Files sub after fully processing the first file via various other subs, the VB Editor apparently doesn't like something about this line: StrFile = Dir(), since it quits after "snapping-back" to the previous sub Initialize(). I have also tried StrFile = Dir, but that doesn't work either. I did Dim Strfile in the General Declarations. When I set Watches for Dir and Dir(), I get the value "Invalid procedure call or argument" for both, as if the directory function lost the value. I can't determine why this is happening.

VB:
Dim WSM As Worksheet, WSB As Worksheet, WS1 As Worksheet, [U]StrFile As String[/U], StrDirectory As String, ClientCode As String
Dim Filename As String, LastRowb As Long, LastColB As Integer, LastRow1 As Integer, NextRowC As Integer, x As Integer, y As Integer

[Code] .......