I recently encountered the following error, when I tried to browse my local svn repository using ViewVC:

SubversionException: ("Can't open file 'c:\\svn\\repos\\db\\current': Access is denied. ", 720005) 

I'm not sure yet, but I think the culprit was committing changes using Cygwin's svn command and the file: protocol. For example:

c:\src> svn co file:///c:/svn/repo/mana
c:\src> cd mana
c:\src\mana> svn ci -m 'from heaven'

To fix it, I ran the following commands:

cacls c:\svn /T /E /G Administrators:F
cacls c:\svn /T /E /G SYSTEM:F
cacls c:\svn /T /E /G Users:R

For some reason

cacls c:\svn /T /E /G %USERNAME%:F

gave the error:

The data is invalid.

To work around this issue, I executed:

cd /D c:\svn
for /R %i in (*.*) do cacls %i /T /E /G %USERNAME%:F

Using the svn: or http: protocols probably do not suffer from this issue. I'll have to remember to use them instead, in the future.

UPDATE:

If I run CollabNet's svnadmin under cmd, cacls reports:

C:\svn\src\db BUILTIN\Administrators:(OI)(CI)F
              NT AUTHORITY\SYSTEM:(OI)(CI)F
              VARUNA\ross:F
              CREATOR OWNER:(OI)(CI)(IO)F
              BUILTIN\Users:(OI)(CI)R
              BUILTIN\Users:(CI)(special access:)
                                FILE_APPEND_DATA

              BUILTIN\Users:(CI)(special access:)
                                FILE_WRITE_DATA

C:\svn\src\db\txn-current-lock BUILTIN\Administrators:F
                               NT AUTHORITY\SYSTEM:F
                               VARUNA\ross:F
                               BUILTIN\Users:R

If I run CollabNet's svnadmin under Cygwin's bash, cacls reports:

C:\svn\src\db VARUNA\ross:F
              CREATOR OWNER:(OI)(CI)(IO)F
              VARUNA\None:R
              CREATOR GROUP:(OI)(CI)(IO)R
              Everyone:(OI)(CI)R

C:\svn\src\db\txn-current-lock VARUNA\ross:F
                               VARUNA\None:R
                               Everyone:R

Another weird Windows anomaly. Just another reason to switch to Linux...