Hi,
I assume you have BlockPeggedExternals set to "true", ie the default value.
Can you test if the following script is an accurate reproduction of what you describe?
[[[
rmdir /s /q repo wc
mkdir repo
svnadmin create repo
svn co file:///%~dp0repo wc
cd wc
mkdir test_library_proj test_library2_proj test_project\somefolder\externals
echo file1>test_library_proj\lib_file1.txt
echo file2>test_library2_proj\lib2_file1.txt
svn add *
svn propset svn:externals "^/test_library2_proj@1 somefolder/externals/test_lib2" test_project
svn propset svn:externals "^/test_library_proj@1 test_lib" test_project\somefolder\externals
svn up
echo change1>test_project\somefolder\externals\test_lib\lib_file1.txt
echo change2>test_project\somefolder\externals\test_lib2\lib2_file1.txt
tortoiseproc /command:commit /path c:\temp\wc
cd %~dp0
]]]
It seems to reproduce the issue you describe.
I stumbled on another bug in the same dialog. Even when a file cannot be checked using the mouse, the "Check: All" function will happily check even the un-clickable file.
Thanks for the report - I will try to take a look at this in the weekend.
Kind regards,
Daniel