Working perfectly, then "Hardware not found"

I just used the "Clear Memory" menu item in the Picaxe programming editor to erase a program on a Picaxe 28X1 on a project board, and now when I try to program the chip (or even to clear the memory again), I get a "Hardware not found" error. Have I somehow ruined the chip? Is there a way to test the board or the chip to see what the problem is?

Thanks for any help.

The hard reset fixed
The hard reset fixed it—thanks for the help!