strange behavior on locks

Hi, 

I running PostgreSQL 8.0.x with database that does not have foreign keys
and sometimes the following messages appears:

ERROR:  deadlock detected
DETAIL:  Process 10029 waits for ShareLock on transaction 65272; blocked
by process 32436.       Process 32436 waits for ShareLock on transaction 65117; blocked
by process 10029.

I also see (right after executing a ps) that there are lots of messages
"select waiting".

1 - Does it mean that process 10029 owns transaction  65117 and 
process 32436 owns transaction 65272 as a transaction acquires an
exclusive lock in its transaction id ?
2 - How is this situation possible ?
What could cause the status ("select waiting") ?

Best regards, 

Alfranio