Encountered various problems with the lucene indexing and reporting in Francotoile, so decided to upgrade from eXist 1.5 to 2.1 in hope that improvements to lucene between those two versions would solve the problems.

I am successfully running an eXist instance on
a Mac running OS 10.7.4
java version 1.6.0_31
Java(TM) SE Runtime Environment (build 1.6.0_31-b04-415-11M3635)
apache tomcat 7.0.21
eXist 1.5.0

I tried downloading and running exist-2.1-dev-rev16458 and am unable.
The catalina log says
"org.apache.catalina.core.StandardContext startInternal
SEVERE: Error filterStart"
If I use the tomcat manager to start exist 2.1 I get
"FAIL - Application at context path /exist21 could not be started"
and the same error in the catalina log

I installed a newer version of tomcat (7.0.27) on that same computer and got the same results when I tried to launch eXist 1.5 (worked) and eXist 2.1 (failed), so I don't think that's the issue.

I then went to a Mac running OS 10.6.8
java version 1.6.0_31
JRE build 1.6.0_31-b04-415-10M3646
apache tomcat 7.0.27

I tried to run exist-2.1-dev-rev16458 and that worked, so it appears to be an issue with the JRE or (less likely) the OS on the first Mac.