Large delay when toggling metronome?

Don't know why this is, but when I toggle either record or play metronome I get a large delay, like 5 seconds. The whole audio engine seems to halt for that period.

I flip the metronomes on/off a lot, some things like touchy feely piano parts no click, other times I flip the play metro just to check the overall feel so It's a bit annoying with the delay.

The rest of Sonar is nice and snappy, any ideas?

I tried adding TTS-1 as it uses little CPU and it's multitimbral GM just to see if it was the default metronome doing this. I set the Sonar metronome settings to "Use MIDI note" and channel 10 so it outputs to the TTS-1 GM drums.

Same thing, toggling the metro on/off, 5 second delay while everything stops dead, UI becomes unresponsive for that period.

I could have it just permanently on and turn it up when needed but then I'd lose count-in.

I get the same kind of delay when record enabling a track, or after going to Sonar options and back out, audio engine just seems to stop and everything is unresponsive for 5 seconds.

Playback is snappy, no delays, dropouts or cracking as you'd get with to low buffers.

I've tried upping the ASIO buffers to as high as they go just to check if that was the problem, but I get the same thing.