When you say "files" do you mean photos? (DSLRs also shoot video.)
If so, yes, as I say in my books and in the FAQs to the right of this forum, you should size your photos to no larger than 1000x750 before you bring them into Premiere Elements. Photos from that camera can be 20-30 times that size.
Steve has covered the still images well. This ARTICLE might give you tips, if you need to batch Scale those.
If you are talking about Video files (MOV with H.264 if they are typical Canon DSLR Video files), then it could be that you are trying to place HD Assets into an SD Project.
Please let us know which types of Assets you are talking about, and also which Project Preset you have chosen.
Thanks, and good luck,
Thanks so much Hunt. This is very helpful. Yes..these are pictures I downlaod to Premier 8. I will check out the link to scale batch them...I have been cropping each picture...reducing size and that worked. Just wanted to find a quick way.
Thanks for that info. I like to do both any Scaling and any Cropping (plus any image editing) in PS first, then doing a Save_As from PS (I just use PSD, the native format of PS), and Import those adjusted files in my video-editing program. Lot less overhead, than pushing a bunch of unnecessary pixels.