Replace Metadata in Bridge CS4 appears to truncate 5.9GB .PSB File; Does CS6 do this too?

Question

I am running Photoshop CS4 on a MacBook Pro with Mac OS X 10.6.8, and ran into a problem with Bridge. I would like to know if this problem occurs with Photoshop CS6. Here's the sequence of events:
1.  I have a 5.9GB .psb file created with PS; it loads into PS cleanly - no errors.
2.  In Bridge, I create a metadata template, and apply it to my .psb file using "Replace Metadata".
3.  The "Replace Metadata" operation completes quite quickly, no error messages
4.  Immediately after the "replace Metadata" operation Bridge reports that my 5.9GB file is now a 1.6GB file - 4.3GB smaller!!
5.  Bridge displays the updated metadata, no visible indication anything is wrong.
6.  Now the file will not open in Photoshop - the read starts, but errors out with "unexpected end of file".
7.  I restore the 5.9GB file and can open it in Photoshop without problems.
Update:
This problem is not specific to the "Replace Metadata" function in the Bridge menu.  I get a similar result by updating the metadata for this file in the Metadata Panel; the resulting file is truncated, but appears to be a different size this time, and it will not open in Photoshop - same error message as before.
This is a 34-image 36856px X 7464px panorama

Answer 1

Thanks for your suggestion, appreciate your effort to help.  The link you provided seems to focus on transfer rates and performance; it does take a while to write or read this file, but I expect that.  I'm not using RAID of any flavour.  I do not expect file corruption, which is what I believe is happening (and PS is reporting).
I have a number of large panoramas; this is the largest.  I believe the largest of the others is a bit over 3GB; I have no difficulty updating the metadata in the other panoramas through the metadata panel or with "Replace Metadata".  All of these files live on the same drive (therefore connected to the same firewire port).  They are backed up to a USB drive with Time Machine, and I've recovered the 5.9GB file from the Time Machine drive a number of times.  I can always read the recovered file with PS, and the size after recovery is always exactly the same.  When I realized that the size of my 5.9GB file changed during/because of the metadata update, I reverted to an earlier stage in the post-processing, got a 3.8GB .PSB and put a copy on DVD; the DVD copy is good, and I can easily and quickly reconstruct the 5.9GB file by applying the same actions used the first time (the 5.9GB file has three layers that are not in the 3.8GB .PSB).  I have not tried to change metadata in the 3.8GB PSB, and can't try that for the next few weeks as I'll be travelling.  The only thing I'm certain of is that updating the metadata in the 5.9GB .PSB reduces the size to 1.6GB (put text in Headline field through Metadata panel) or 1.4GB ("Replace Metadata" in Bridge Tools menu), depending on how the update is done.
So, the 5.9GB file has survived several complete transfers (PS=>Disk, Disk=>Time Machine, multiple Time Machine=>Disk, PS=>Disk to 3.8GB after deleting layers, and Disk(3.8GB)=>DVD) with no signs of corruption.
It's very hard to accept the idea that there's some kind of hardware problem that afflicts just one file.  The 5.9GB file is output from PS CS4, and I can read it back into PS with no problem. 
I'll watch this forum for a few days to see if there are more answers until I have to travel.  If not, I'll figure it out another way and report a bug in CS6 if that appears to be appropriate.