i will put my experience with this bug here altough i think this would
better belong to ib-support or firebird-devel.
i think i was hit by this problem recently, i have asked for help in
ib-support under the title "ibserver running at 100%". the cause of all
these problems mentioned there was one little thing: i had two java programs
connecting to the database. one from localhost, one from another host. the
program that connected from the other host was some kind of
data-insert-program. after running this program the records did not appear
in the database, altough they were successfully inserted and commited by the
data-insert-program. additionally, "wrong page type" errors appeared in the
database. i had to backuprestore it or it would lose all data after some
additional time. after two days of intensive search i found the problem by
looking at the server properties/log page in ibexpert. i noticed that the
same database was open twice by the server, so it was like the server
accessing two different databases, but in fact it was the same file, hence
the corruption problem! the output looked like this:

Database Info
---------------------------------------------------------------------------
Number of connections: 17
Number of databases: 2
Databases: /opt/interbase/databases/agro.gdb
opt/interbase/databases/agro.gdb


this occured using firebird 1.0 SS on linux. the problem was, that the two
clients connected to the server with two different connection strings:
jdbc:interbase://localhost//opt/interbase/databases/agro.gdb
jdbc:interbase://localhost/opt/interbase/databases/agro.gdb

so this little slash missing was causing us very heavy problems with the
database. after i made sure that all clients connected using the same string
with the / all problems disappeared.

regards
michael weissenbacher