Sounds coming from the bike like you described can be a little difficult to pinpoint because sounds will telegraph through the frame and your hearing is affected by the air moving past your head. Experience lends a lot to this type of situation.
If you think it might be the spokes then check your spokes for tension. Spokes can make a "pop" sound. I can't comment on the danger, Fox Rider. If you have a concern about safety and you don't feel qualified to ensure the soundness of your bike, then by all means take it to the LBS. I'll bet they can find the source of the noise if you can show them how to recreate it.
Bottom line: If we here playing on the web can't ride the bike or hear the sound then there's only so much that can be offered as likely possibilities.