can't load $somepath/LibXML.so for module LibXML: $somepath/LibXML.so undefined symbol: xmlIsBaseCharGroup at $someotherpath/DynaLoader.pm line $num

problem that seems to occasionally occur? Namely once you've got a working libxml of an appropriate version, rebuild BOTH XML::LibXML-Common and XML-LibXML, and if that doesn't work start looking at library paths? This stumps me every time I install LibXML on our oldish RedHat servers for at least half an hour - hopefully writing this will mean that I, at least, won't have problems next time.