We have virtual-hosts in server.xml with aliases of more than 40 characters. No problem on the jboss side, but on apache side, mod_cluster fails with the following message : "MEM: Can't read host alias".
Changing HOSTALIASZ from 40 to 64 (mod_clustersize.h) resolves the problem (see patch #1).

NB: I had to fix a few "NMAKEmakefile", otherwise it won't compile with Visual Studio 2010 (see patch #2)