I don't know enough to tell whether it is a jade bug or a stylesheet bug. I have various odd problems rendering tables with the tex backend. Html renders fine most of the time; my only issue with html is that the stylesheet doesn't honour colsep and rowsep attributes, but I can work around that issue with post-processing. For the tex backend, the best illustration of the problems I have is the table example at http://www.docbook.org/tdg/en/html/table.html
I have attached two versions of this example (the original docbook.org version and a slightly modified one with fixed column widths).
I am trying to build it with XML-Docbook V4.1.2 and its corresponding stylesheet from current ubuntu repositories. Openade version is:
openjade:I: "openjade" version "1.3.2"
openjade:I: "OpenSP" version "1.5.2"
I could not build the current svn version of openjade because of multiple autotools errors.
The first Issue is illustrated in the original docbook example, found in "jade-test.1". I get overfull \hbox, and part of the table overruns the page. In some other cases, when the table structure is simpler, there is typically a smaller overrun, but even a single-cell table overruns the page width by a few points.
The second issue is that the cells spanning multiple rows or columns break the table structure, and sometimes the entire table disappears (of which I can provide an example, although not a simple one). This is also well illustrated by the docbook table example found in "jade-test.2". It has the same structure as that in "jade-test.1", except for the fixed column widths, which I used to make the table fit on the page. While setting the widths, I also noticed that they do not add up. For example, setting all colwidths to 50pt will mangle the first couple columns.
examples of broken docbook table rendering