Try to install PostGIS 2.0 from svn in Ubuntu 11.04. After running postgis.sql file I get an error:
ERROR: could not load library "/usr/lib/postgresql/9.0/lib/postgis-2.0.so": /usr/lib/postgresql/9.0/lib/postgis-2.0.so: undefined symbol: DirectFunctionCall3Coll
PostGIS 1.5 installed without any problems.
GSERIALIZED_ONchange) – Mike Toews Jul 3 '11 at 23:31