Start with #2 on Spot's list. If you do any of the blurs, your pics may start to look too soft. With Gaussian, you may be able to get by with just vertical set to 0.001, and not horizontal.

Also, before you try any of the blurs, if #2 (reduce interlace flicker) doesn't work, try using your photo editing program to reduce the resolution, especially if you are not zooming in very much with pan/crop. If you start with super high-res (like 3000x2000 or higher), this not only takes Vegas a lot of time to deal with, but it can cause flicker as the images are down-sampled to 720x480 (for NTSC DV). If you do reduce the resolution, remember to first save your original, high-res versions, in case you need them for something else. Also, if you are saving back to JPEG, set the quality setting in your photo editing program way up to the maximum so you don't lose any quality by re-compressing an already compressed image. This will result in a much larger file, but that doesn't matter to Vegas, because regardless of the amount of compression in a JPEG file, the file size actually used inside of the application will always be determined by the resolution, not the size of the file.