A PHOTOGRAPHER FRIEND

6.29.09 I am sure this is not my first nor will it be my last photo that I am desperate to understand what I have done wrong. This was a group shot at a party yesterday. I struggled all day getting bright enough exposures..sharpness almost everything. Tonight I am looking at the photos more carefully on the computer and am just about in tears. This was the first time anyone ever hired me and paid me to shoot an event and they are undoubtedly the worst photos I have taken in years!!! Why are they so grainy? You can see the photo information. Maybe I should have used an additional flash ( duh...I have the 580 ex ll, I just got, but do I use it?) Do you think it was the lack of good flash? I have others and so many are out of focus and lots of noise, even ones I took outside had lots of noise. Could it be my lens or the camera? I've never had such a bad lot..any advice or help will be greatly appreciated. Thanks!

6.29.09 I am sure this is not my first nor will it be my last photo that I am desperate to understand what I have done wrong. This was a group shot at a party yesterday. I struggled all day getting bright enough exposures..sharpness almost everything. Tonight I am looking at the photos more carefully on the computer and am just about in tears. This was the first time anyone ever hired me and paid me to shoot an event and they are undoubtedly the worst photos I have taken in years!!! Why are they so grainy? You can see the photo information. Maybe I should have used an additional flash ( duh...I have the 580 ex ll, I just got, but do I use it?) Do you think it was the lack of good flash? I have others and so many are out of focus and lots of noise, even ones I took outside had lots of noise. Could it be my lens or the camera? I've never had such a bad lot..any advice or help will be greatly appreciated. Thanks!