The 1.9.0.548 version has all the x64 compatibility fixes turned off. This was done to make sure that none of those x64 specific changes (that are not yet fully tested) cause any problems to the majority of users who use 32 bit operating systems.
The work on the x64 compatibility will continue after this release, and hopefully the next release contains full x64 compatibility. No need to do any further 64 bit testing on this version.
