<guessing>
Assuming PVD (er, Delphi) uses the MSXML library for parsing, there are different versions available. A quick look at your windows/system32 directory should tell you which versions you have loaded (3,4 and 6, being likely for 64 bit and 3,4 for 32 bit...and 6 on XP SP3 or later). If these DLLs are the same on all systems, I'm out of ideas for the differences.
The narrow left column can't be reproduced on my system...Vista 32 bit (MSXML versions 3,4,6) and PVD 0.9.9.21. It does make sense to me though...
The control tries to use the minimal amount of space because it's being autosized. For a title, it would use the minimal width necessary to display the title. For a multi-line display, it makes sense to look at the height of the page, then make the control's width whatever is necessary to fit the text into the display. This would account for differences encountered with expandable fields.
Rick's comment that a refresh resolves the issue also makes sense, if the parser invokes the renderer in real time...the renderer won't know about other tabs or columns that might occur later in the XML code. Once the page has been parsed once, all the page elements are known, so the renderer can make a better decision.
</guessing>
The obvious fix would be to assign a width to the control or to one of it's parent containers (page control would be my preference). If that works, it doesn't mean there isn't a problem, just that there's a work-around for it.
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