Canon EOS Stops Taking Photos

Hi Guys,

Hope someone can help. I have a Canon Digital Rebel EOS camera that I
really like. Here's my question. I was shooting at a 1 year old's
birthday party last night in a restaurant (Casa Bonita) and there
where times where the shutter would not trigger. My assumption is that
the camera thought it was too dark or couldn't find any focus points
or something. When I'd press the shutter, I'd see a "Busy" in the
viewfinder and a fully colored circle in the display. I had a problem
with a Sigma lens getting an Err99 but that is off to be fixed and I
can't think of anything related between these events. It's like the
DSLR just goes to lunch sometimes. Oddly powering off/on would no
avail, but I did get a reset removing the battery.

Any help or thoughts very, very much appreciated.

Sincerely,

Tim