Does the install claim anywhere that there is a 64bit version in the install package?
We run a lot of very expensive packages on Solaris 11 64bit systems, that are in fact 32 bit. All run fine, obviously. And interoperate with 64bit images as well.
I was on the linuxquestions forums earlier asking about this. And one of them successfully compiled a 64bit murrine theme engine on Linux. So I know its possible.
The 32bit library works great in Solaris for most of the apps. But Java apps use the 64bit version.