Ok, so I did some testing, and am not sure where to go from here:

1)  I went to "Build -> Rebuild Website" in the Visual Web Developer 2005 Express menu. 

2)  After the site was done rebuilding, I logged in to the DNN instance created on my ASP.Net Development Server and navigated to my custom  module.  No change in how the Action items look.

3)  So, I closed the site and opened the /bin file of my project, then checked the date of the .dll.  "Modified" date is 1/10/07. No change here either.

4)  I ran a search on my hard drive for the .dll and could not find any other versions.

5)  I double-checked the "Development Environment" specified in the DNN "Modules" pdf as you suggested, and I'm pretty sure I've got it set up as specified.

Any suggestions on where to go from here?

smcclure11,

Thank you VERY much for your help, and sorry it took me so long to reply (busy week)!  Your solution to my problem was spot-on.  I took a bit of a shortcut on your proposed setup, but I'm sure either way would work. 

I only created the first project you suggested, then added the appropriate references, then added my .vb files as "Existing Items".  Next, I  edited the "My Project" properties to make sure the "Name", "File" and "Assembly" versions of the old and new .dll would match  Finally, I go to the VB Express Main Menu and select "Build -> Build MyCustomModule".   It dumps the new .dll into the project's \bin directory, so I still have to Copy & Paste it into my DNN\bin, but it does the job and now changes made to my .vb files are working!  Perhaps I'll look into implementing your setup now that the site is functioning correctly again.

Thanks again for the help.