Can't reproduce that. All titles/captions of a multi-file export are retained. Also 5.2 on Win7.
How are you checking?
I noticed it when I was uploading files to a POD site I use. I thought initially that I'd forgotten to tag, but I checked LR, and sure enough all text was present. So I used Window Explorer to view the file details and there were keywords, but no title or caption. Re-exporting the file on it's own solved it, but if I export in a batch it strips that info from all except the first image.
Very strange. Haven't heard of any similar reports, so it doesn't sound like a very common problem. Maybe try resetting your preferences file, but if that doesn't work all I can suggest is to raise the problem at the official Adobe feedback site.
For resetting the preferences file, see here: