Well since I first created a loca Liferay instance and then paid for Rimu hosting we've gone from v4.1.2 to 4.1.3 and finally to 4.2 Sadly none of these versions has a document library that works which is disappointing for a standard install of standard portlets using the hosting service advertised on the Liferay site. In their defence, it works fine on my local instance although that was a slightly earlier version of the ENTERPRISE version (can't remember which) and it was using the Hypersonic Db that came with the Tomcat/JBoss install file (as used in the Lifecast I think).
There are some relevent issues logged on the Liferay forum with some rather cryptic fixes, apparently the issue is a deprecated method in Lucene (apache) that is called by Jackrabbit (apache). In any case, the fix seems to be incomplete (or I'm being thick (likely)) and it was not fixed in two upgrades.
The folks at Rimu are very helpful but understandably don't seem keen to be debugging/fixing the java issues - it seems that the relationship between the two organisations is not as close as I would have hoped. Perhaps a lot to expect, Liferay is quite a sophisticated beast and getting into the detail would require quite a big investment in time, as I'm discovering.
I've now mailed the Liferay Sales team requesting assistance twice and an awaiting a reply.