: Unless I'm doing something wrong, in my experience in multi-core Solr in : 1.4.1, you NEED to explicitly provide an absolute path to the 'data' dir.
have you looked at the example/multicore directory that was included in the 1.4.1 release? it has a solr.xml that loads two cores w/o specifying a data dir in the solr.xml (or hte solrconfig.xml) and it uses the "data" dir inside the specified instanceDir. If that example works for you, but your own configs do not, then we'll need more details about your own configs -- how are you running solr, what does the solrconfig.xml of the core look like, etc... -Hoss
