This page points to installers for 32 bit and 64 bit operating systems. Please make sure that you choose the right installer for your PC. Otherwise the setup will fail.
We got reports that upgrading sometimes does not work properly. If you have problems after updating TortoiseSVN, just uninstall it, reboot, and then install it again.
Note for x64 users: you can install both the 32 and 64-bit version side by side. This will enable the TortoiseSVN features also for 32-bit applications.