STM32L - Debugger quits when clock is too low

When I'm working with the STM32L Discovery, if I use MSI as the SysClock and it's set to 65KHz, the debugger just quits. If I re-plug the board, it won't connect until I do a chip erase using the ST-Link utility. It seems to work fine at 130KHz though.

Any one else encounter this?