Nope, I learnt with a film SLR many moons ago, I had the 350D for a year and a half too so I am fairly confident that it is not down to user error... although you never know! I also took a load of shots at f8 and f16 last night with the flash to test it but did not get a chance to go through them on the PC.
Tried both Raw and Jpeg too as Raw are notoriously less sharp due to the lack of camera processing. I think I am just looking too deep into the image TBH but it is just something that is nagging me.