That shouldn't happen, a class 6 SDHC card should be plenty fast. I'm only using a not-so-special class 4 SDHC with my Pentax and I can burst fire at least 10 pictures before the buffer fills.
Does the camera actually not allow you take a picture (you press the shutter and nothing happens), or are you waiting for the picture you just took to appear on the LCD? Basically, a camera stores the picture in a memory buffer until its full, all the while writing to your SDHC card any pictures you've taken in a recent burst. Just because a picture isn't yet on the LCD, or the card-writing light is blinking shouldn't mean you can't take another picture. At least that's how it is for DSLRs.
If you actually can't take a second picture relatively immediately, then check the settings to make sure there's no heavy processing parameters being used (color adjustments, noise reduction, etc...). Also check for any settings that might interrupt your LCD, like an auto-preview or something.
I know there are some people with the same camera on this board. Hopefully they'll chime in.