I really have a problem, I have a VS 2010 solution and it suddenly stopped debugging for referenced projects, I just can debug the start up project but not the added as reference. This is weird because I created a new solution, added two projects and then I debugged in both successfully, did that in order to see if my VS config was wrong, but nop, It's something on this particular solution that is not allowing me to debug referenced projects.
I've read all possible solutions from this forum and other sources like Microsoft. If I go to menu Debug -> windows -> Modules the ones I want to debug are not in the list. 
so, I read a Microsoft's page saying how to manually load symbols, I did the following:
To specify a directory where symbol files are located
On the Tools menu, choose Options.
In the Options dialog box, open the Debugging node and then click
Symbols.On the Symbols page, there is a box that states Symbol file (.pdb)
locations. Above the box are four icons.Click the folder icon.
Editable text appears in the Symbol file (.pdb) locations box.
Type the directory path. Statement completion helps you find the
correct format.If you are doing remote debugging, symbol files and symbol server
caches for managed code must be located on the remote computer. Symbol
files and symbol server caches for native code must be located on the
local computer.If you are using symbols on a remote symbol server, you can improve
performance by specifying a local directory that symbols can be copied
to. To do this, type a path in the Cache symbols in this directory
box. If you are debugging a program on a remote computer, the cache
directory refers to the directory on the remote computer.Click OK.
That didn't work, I still can't see the modules I want to load so.. any ideas my friends ?
Best Answer
One more thing to check, just to be clear: Make sure you have the configuration set to 'Debug' and not 'Release'. You can debug the startup project in 'Release' mode, but not a referenced class library.