Previews not showing up in Library module for photos in one catalog

[Clyde_Lovett]

Lightroom v3.4.1

Apple iMac 2.4 GHz Intel Core Duo

OS 10.7.2

As per my subject line: previews not showing up in Library module for photos in one catalog.  So thus, in grid view the thumbnails are gray, although file (name, size, etc) and modification information appears (icons for keywords, adjustments, etc.).  When I click on any grayed out thumbnail I notice that on my second monitor, in Loupe view, it reads the file name (the information in the top left) but where the photo would normally appear there is only the text "No photo selected."  Obviously there IS a photo selected.  The same issue occurs when grid on the second monitor and Loupe on the main monitor. 

Oddly enough, if I switch to develop mode the image loads in both thumbnail and full size and sticks when I return to Library mode. 

I have tried deleting (and thus recreating) <catalog name> Previews.lrdata

I have tried creating a new montior profile.

Obviously, not with success.

This problem is localized to THIS catalog and so, yes, it makes me wonder if the catalog is corrupted or something horrible. 

I tried using a backup but had the same issue so perhaps I need to go further back in time ...

I use Lightroom heavily and so I hope that I do not have to lose my catalog of 45,000 adjustments ...

Any help / suggestions would be greatly appreciated!

[defaultp7pxwv43ym1d]

this one fixed it for me thank you!