The mod Powered Belts (0.4.0) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event PoweredBelts::on_tick (ID 0)
invalid key to 'next'
stack traceback:
[C]: in function 'next'
PoweredBelts/control.lua:50: in function <PoweredBelts/control.lua:46>

The mod Powered Belts (0.4.0) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event PoweredBelts::on_tick (ID 0)
invalid key to 'next'
stack traceback:
[C]: in function 'next'
PoweredBelts/control.lua:50: in function <PoweredBelts/control.lua:46>

Placed my first belt down and received the above error.

No idea what could be wrong, it works fine for me. Was this on a new save or an existing one?

New save, it could have something to do with Bob' burner stage setting for basic belts. In any case great mod