Greetings,
It is possible you have one or more corrupt images / movies in your camera roll which is upsetting the import process in iPhoto.
To try and resolve your issue:
Ensure all your software is up to date (Apple Menu > Software Update).
Remove the following to the trash and restart the computer and try again:
Home > Library > Caches (I remove the whole folder. It will be re-generated upon restart.)
Home > Library > Preferences > com.apple.iPhoto (There may be more than one. Remove them all.)
If the issue persists try rebuilding your iPhoto Library following this article
http://support.apple.com/kb/HT2638. Use the bottom 3 rebuild options.
If the issue persists these jpeg files may be damaged. Try importing them using Image Capture found in Macintosh HD > Applications.
If Image Capture can import them you can then try to add them to iPhoto.
If you still get the same error message try opening the files with Preview by double-clicking on them. You can then go to File > Save As > Format > TIFF and add those files to iPhoto.
When you import pictures from the iPhone to iPhoto you are offered the option to delete the images post-import. Like iPhoto, Image Capture will also allow deletion of items in the camera roll post-import. Check off the option to "delete after import" in the bottom left of the Image Capture window.
For questions on using the iPhone itself consider posting in the iPhone forum
http://discussions.apple.com/category.jspa?categoryID=201.
Hope that helps.