“The breakpoint will not currently be hit. No symbols have been loaded for this document.” by Doug Butscher

Probably a DLL in your GAC does not have the same symbols which are in your dev bin folder. Overwrite the DLL with your development one and most probably the error will be gone.

Also be aware that in Sharepoint solutions GAC DLLs can be locked by VS.NET, please check the following link:

http://alexangas.com/blog/2009/07/debugging-file-locking-in-the-gac/

“While debugging in Visual Studio, click on Debug > Windows > Modules. The IDE will dock a Modules window, showing all the modules that have been loaded for your project.
Look for your project’s DLL, and check the Symbol Status for it.
If it says Symbols Loaded, then you’re golden. If it says something like Cannot find or open the PDB file, right-click on your module, select Load Symbols, and browse to the path of your PDB.
I’ve found that it’s sometimes necessary to
stop the debugger
close the IDE
close the hosting application
nuke the obj and bin folders
restart the IDE
rebuild the project
go through the Modules window again
Once you browse to the location of your PDB file, the Symbol Status should change to Symbols Loaded, and you should now be able to set and catch a breakpoint at your line in code.”
quote from http://geekswithblogs.net/dbutscher/archive/2007/06/26/113472.aspx

“Debugging in Visual Studio .Net 2003
Am i stupid? No i´m not! But now and then i make stupid mistakes. This is defenitily one off those which costed me an awfull lot of time!
What happened? Suddenly, without any obvious reason, i could’t debug in Visual Studio .Net 2003 anymore. I didn’t do anything, it just happened. (that’s what i thought. Yes i know; nothing ever just happens, but …)
When i started debugging i saw for the system dll´s “No symbols loaded”.
For my own dll’s “No native symbols in symbol file” appeared. This didn’t ring a bell!
So i started looking on the net, couln’t find anything that helped me. …
And then, after … i don’t want to tell you how much time i lost with this, despite all, i started debugging again, looked at the popup that you get when you press attach to a proces, and saw that only “Native” was checked and not “Common Language Runtime”.
Aaaaahhhh! In the beginning i was really desperate, but now, five fingernails later, i’m glad i found it! Finally i will sleep again tonight!”