The CollabNet Desktop for Windows is a 32-bit application. If you have a 64-bit Windows operating system with a 64-bit version of TortoiseSVN, you will not see the TortiseSVN options for an item in the File System Explorer.
The workaround is to install the 32-bit version of TortiseSVN. From http://tortoisesvn.net/downloads: x64 users can install both the 32 and 64-bit versions side by side. This will enable TortoiseSVN features for 32-bit applications also.