I have the same problem. OS X 10.7.4
I have followed the technote, but I don't have any user presets in the develop module. I created a new catalogue and imported from the failing catalogue. No problems with 'Assertion Failed', but I don't have my facebook and flickr publishing defined (Not transferred during import).
So from this I can only assume that it is the publishing plugins that are causing the problem! But, I use this alot and shouldn't have to recreate all the published collections. I have tried the other suggestsions of deleting the lightroom 4 plist and clearing the cache folders, still no joy!
So, does anybody else have any suggestions as to how to fix this without recreating new catalogues and losing all the predefined publishing collections!!!
After talking to Adobe support, they say that because LR4 has so many new features the catalog update doesn't always operate correctly!
Nice one adobe, provide an update path that "doesn't always work"!!!
The only way around it is to create a new catalog and import all the pictures from the failing catalog. In the process losing all published services! Not ideal but I'll have to live with it.
Surely the "assertion failed" message could write out to a log stating exactly what caused the fault. In the apple console all you get is
"31/05/2012 13:49:23.006 Adobe Photoshop Lightroom 4: Oops! An untagged string (assertion failed!) got thrown far enough that we display it to the user. This shouldn't happen."
Come on Adobe this is poor!!!
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