We use Linux for our web search index (created by full Texis installation) and we have hit the same problem. Is moving to Solaris (it has to be unix...) the only way out of this?
We do have versions of the full Texis product that can handle 64-bit files on the following platforms: Alpha-Tru64, Solaris 2.6+, Linux 2.4+, Windows NT/2000/XP and FreeBSD.
You would need to convert the files to the 64-bit format.