libxslt port build problem

[Colin]

Hi,
I've been unable to upgrade libxslt for a while on my installation of 
FreeBSD 7.0-RELEASE-p12
It always tells me the following:

checking for libxml libraries >= 2.6.27... configure: error: Version 
2.6.23 found. You need at least libxml2 2.6.27 for this version of libxslt

I can find no information on where it is getting the information that 
2.6.23 is installed because pkg_info shows only libxml2-2.7.6 (the 
current port) as installed.

I don't really know anything about libxml2 so I assume there's some 
leftover bits from an old version somewhere..can you point me in the 
right direction to clean it up?

Thanks
Colin.