It is very most likely your technique.
It is a common complaint by many photographers using many cameras - as many do not have correct High ISO / Available Light Techniques.
As said before in this thread you CANNOT underexpose when using High ISO, but a quick glance of the thread and none yet have a 450D to exhibit.
This is a 400D (previous model to yours), purposely chosen as this image was made shooting INTO the light whilst in dark area and the scene has a large dynamic range:
©Image copyright JVW 2010, used with permission
"Solo Prayer - Turkey 2010"
Tech: EOS400D EF35F/2
Shooting: F/3.5 @ 1/100s @
ISO1600 Hand Held, Available Light.
And the Crop:
***
The EOS60D and EOS7D will perform better at high ISO, than the EOS450D
WW
Footnotes:
1.
Ref 400D vs. 450D High ISO Comparison.“There's little visible (or measurable) difference between the EOS 450D and its predecessor [EOS400D] at higher ISO settings, and both show Canon still has a slight edge over its rivals at this end of the market (thanks to superior processing and a more light-handed approach to noise reduction.” (
www.dpreview.com)
2.
REF: http://www.dpreview.com/reviews/canoneos450d/page32.asp