First, starting with 2578 (maybe earlier) closing down interface leaves the DDE.exe process running, consequently newer installs fail until DDE is manually terminated.
Second starting somewhere after 2578 up to and including 2584, it crashes within several seconds after launching it. This is on Win7 ultimate.
No symbols, so not much more than this null pointer access:
Unhandled exception at 0x00A9FC15 in interface.exe: 0xC0000005: Access violation reading location 0x00000000.