Good to know, its helpful to have this extra context. My concern is that some part of VML doesn't behave well when loaded in this way, perhaps an extra necessary stylesheet is missing. I've moved this to the bugs forum, and we'll look into it further.
I try to spend about half a day a week fighting with this, and this week am consulting with other chart/draw experts at Sencha but so far we've got nothing. Something *appears* to be wrong with how IE is applying the namespace - it applies it in some cases (all TextSprites work), and doesnt work in others. If we leave out either the namespace wiring or the ie-specific behavior CSS, it completely breaks (as expected), but if I just disable the behavior and reenabled it, all elements render correctly... until any element changes, in which case it is invisible again.
No one I've talked to has ever seen a case quite like this, and most of MS's own VML documentation is at best internally inconsistent and at worst gone and replaced by useless 404 pages.
The especially frustrating part to this is that the only change required to cause this issue is to change the linker, which merely modifies how scripts are injected into the page. My next step may be to make my own linker, or manually copy large swaths of generated GWT js into handmade js files and boil it down into just a few lines to try drawing a single element.
This is one of the most frustrating IE bugs I've faced in quite a while, which is why I'm posting on my lack of progress here - there isn't a viable workaround, and there is no apparent reason why it isn't working with one linker, but is with another.
Other things I've tried:
-reordering injecting css vs adding the namespace
-using external css or style tags in place of CssResource
-other standard gwt linkers, only std works, all others i've tried (direct_install, xsiframe, sso) have the bug. Worth nothing that direct install extends xsiframe, but sso is totally on its own, and in fact is only one step instead of two (just a .nocache.js, no additional external files)
-three-arg instead of two-arg namespaces.add (gxt uses the two-arg by default, whereas http://stackoverflow.com/a/3891060/860630 says that only the three arg works)
-out of desperation, changing the namespace to see if it miraculously fixed it. Nope.
I'm open to suggestions, and will continue slowing grinding away time on this, but I'm not optimistic after this many weeks of 10% of my time on this.