I have experienced something very weird.
I am using SQL-Ledger and for a long time experienced problems with the CGI based solution on my MacBook Pro running OS X.
The problem has been internal server errors when posting, but the posts went through so I sort of survived.
I have not been able to locate the problem and I was slowly giving up on SQL-Ledger, which is both open source and free.
The mailing list was not able to provide any answers and I had been look at alternative account packages since working with a dysfunctional SQL-Ledger was quite tiresome.
So now I have updated to Leopard and the problem magically went away.
So again I am a happy SQL-Ledger user.