For more than a year, getting icon overlays to work with both TortoiseCVS and TortoiseSVN on x64 has been a nightmare.
First, install the latest stable TortoiseSVN.
Then install my custom build of TortoiseCVS, TortoiseCVS-1.11.6-pardini.exe. It is a custom built CVS-HEAD checkout, without many changes.
Please note that apparently TCVS is the one that decides the icons to use (both TSVN and TCVS will use the same icons), but they all work.
If it’s not working for you, uninstall all TortoiseSVN, TortoiseCVS and TortoiseOverlays you may have installed.
Also delete the registry key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\ShellIconOverlayIdentifiers.
Then reinstall in the order I suggested above.