vacuumdb not enough stack items

Hi,

i use postgresql version7.4.7 on i386-pc-linux-gnu, autovacuum is
configured to run on this database.
But recently, we lost data for a database, we were able to connect the
database but we couldn't see any table anymore.
I suspected a transaction ID wraparound, and to fix it, i just
imported data from a dump file.
I tried to execute the following  query:
SELECT datname, age(datfrozenxid) FROM pg_database where age(datfrozenxid)<0;
template1=# SELECT datname, age(datfrozenxid) FROM pg_database where
age(datfrozenxid)<0;
                  datname                  |     age
------------------------------------------+-------------
  template0                                |  -597653514
  ez_info1                                 |  -205024652
  XtDB                                     |  -205024658


Does the negative value of age means that a transaction ID wraparound
has already occured?

Doing a manual vacuumdb on each database raise an error message saying:
vacuumdb: vacuuming of database "ez_info1" failed: ERREUR:  not enough
stack items

Have you an idea about what is happening,

Thank you for any suggestion.