1000 x 750 pixels is the usual maximum size advice
I have some panas in the 1.5GB to 2.0GB range.
Did you try importing 1-at-a-time?
What are your system specs?
When it comes to size limits for video editing software, DPI doesn't got much to do with it, it's usually the number of pixels that counts.
Anyway, maybe this link will help:
(PS! Before, it used to be 4000 x 4000 pixels, I'm still on CS3, but happy if Premiere now supports more pixels)
EDIT: Just discovered it was "by Todd Kopriva", which usually (mildly said) means you can take the info (in the link) for granted.
For Video, DPI, and PPI, are meaningless. It is only the pixel x pixel dimensions, that matter. **
In earlier versions of PrPro, there was a 4096 x 4096 pixel limit, IIRC, but CS5 bumped that up. CS5 also improved the Scaling algorithms, when using large stills and Scaling them down to the Project's Frame Size *. However, large stills require overhead to process. Many overly large images will bring even a stout machine to its knees.
In general, I Scale to my Frame Size, in Photoshop, prior to Import. This ARTICLE will give you tips on automating that process. With CS5, disregard the comments on quality of Scaling algorithms. That has changed. Also, that article was written back in the SD days, so references to 720 x 480 can now probably be upped to 1920 x 1080.
The only reason to go much larger than the Frame Size of the Project would be to Pan on a Zoomed out image. When I plan on doing that, I calculate the exact Scale that I will need, and Scale/resize to that dimension in PS. Also, if I am only doing a lateral/horizontal Pan, I will then Crop out unnecessary vertical pixels, to keep the overhead to a minimum.
Good luck, and hope that helps,
* Thanks to Todd for that info
** Oops, Dag beat me to it. Did not see his reply, when I posted