Some files get checked out read-only in WinCVS

Check your umask. Set your umask to 0001 in .bash_profile file in your Cygwin home directory.
Note:
1. If your umask is 022 your files will be 644.
2. If your umask is 02 your files will be 664.
3. If your umask is 0 your files will be 666.

Uncheck the ‘Checkout read-only’ option in WinCvs Preferences or in Checkout settings -> Globals