I've shot a mix of 12-bit and 14-bit, always with lossy compression and CS3 seems just fine. I wouldn't want to access them over the network though, they're on a local RAID-5 array. I can't see any difference between how D300 and D2x NEF's are handled by CS3 on my system.
Are you using central/global cache or distributed? I use the latter because I learned a version or two back that the centralized cache had a tendency to be problematic.
I'm running Vista x64 on quad-core with 8GB of ram.
Th D2X NEFs are fine - and I have lots of them. The D100, D70, and D200 NEFs all behave perfectly.
The D300 NEFs are the only problem of all the Nikon models. Another problem - the cropping is not properly viewed in the Bridge CS3 thumbnail. Very strange.
The cache is set to 'Export to folders when possible"
The cache size to large.
I even purged the cache 'manually' and deleted the in folder cache without any improvement.
The network is very fast (1000MB/sec, duplex switch), as is the server (Raid 5, 10,000rpm drives). As I listed on the previous post, even locally downloaded files behave in the same way - so its not a network performance issue (although, I did think that at first, as well!)