I do have precisly the same problem.

That means IPN worked when I used 1.3.6. After I upgraded to 1.3.7 everythin was fine in the beginning but than started a problem. When Ordering through IPN custumer is directed to PayPal and pay as normal, he is than redirected to the Checkout-Success page without displaying an error. No Order is recorded and the basket is empty.

Here is my IPN log of my last try:

Code:
Jan 12 2007 12:40 -- Breakpoint: 1

Jan 12 2007 12:40 -- Breakpoint: 2

Jan 12 2007 12:40 -- Breakpoint: 3

Jan 12 2007 12:40 -- IPN WARNING::Could not find matched txn_id record in DB

Jan 12 2007 12:40 -- Breakpoint: 4 txn_type=unique ordersID =  IPN_id=

Jan 12 2007 12:40 -- IPN DEBUG::uniqueness-test.  Relevant data from POST:
txn_type = unique
parent_txn_id = 
txn_id = 57J15009F9790130P

Jan 12 2007 12:40 -- IPN NOTICE::Set transaction type = pending-echeck
POST data:
mc_gross=34.95 
&address_status=unconfirmed 
&payer_id=AK2xxxxxxxxxxx
&tax=0.00 
&address_street=Donxxxxxxxxxxxxxxx
&payment_date=03:39:15 Jan 12, 2007 PST 
&payment_status=Pending 
&charset=windows-1252 
&address_zip=4710 
&first_name=Ariane 
&address_country_code=BE 
&address_name=Dieter Brandenburger 
&notify_version=2.1 
&custom=zenid=f91f80f3fa2c9748889b225824c32266 
&payer_status=unverified 
&business=admin@txxxxxxxxxxxx
&address_country=Belgium 
&address_city=Lontzen 
&quantity=1 
&verify_sign=AUaxvSoxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx 
&[email protected] 
&txn_id=57J15009F9790130P 
&payment_type=echeck 
&last_name=Brxxxxxxxxxxx 
&address_state=0 
&receiver_email=admin@xxxxxxxxxxxxxxxx 
&receiver_id=QGWEEHNU35J7S 
&pending_reason=echeck 
&txn_type=web_accept 
&item_name=DREHMAHL - Shop Einkauf 
&mc_currency=EUR 
&item_number=1 
&residence_country=DE 
&payment_gross= 
&shipping=0.00 
&cmd=_notify-validate

Jan 12 2007 12:40 -- Breakpoint: 5 txn_type=pending-echeck

Jan 12 2007 12:40 -- IPN WARNING:: Could not establish txn type pending-echeck
 postdata=mc_gross=34.95 
&address_status=unconfirmed 
&payer_id=AK2CQ72SQDESS 
&tax=0.00 
&address_street=Doxxxxxxxxxxxxxxxxxxx
&payment_date=03:39:15 Jan 12, 2007 PST 
&payment_status=Pending 
&charset=windows-1252 
&address_zip=4710 
&first_name=Ariane 
&address_country_code=BE 
&address_name=Dietexxxxxxxxxxxxxx
&notify_version=2.1 
&custom=zenid=f91f80f3fa2c9748889b225824c32266 
&payer_status=unverified 
&business=admin@xxxxxxxxxxxxxxx 
&address_country=Belgium 
&address_city=Lontzen 
&quantity=1 
&verify_sign=AUaxvSojqajxsiGA9qxxxxxxxxxxxxxxxxxxxxx 
&[email protected] 
&txn_id=57J15009F9790130P 
&payment_type=echeck 
&last_name=Bxxxxxxxxxxxxxxx
&address_state=0 
&receiver_email=admin@xxxxxxxxxxxxxxxxxxx
&receiver_id=QGWEEHNU35J7S 
&pending_reason=echeck 
&txn_type=web_accept 
&item_name=DREHMAHL - Shop Einkauf 
&mc_currency=EUR 
&item_number=1 
&residence_country=DE 
&payment_gross= 
&shipping=0.00 
&cmd=_notify-validate
I only find a warning

Jan 12 2007 12:40 -- IPN WARNING:: Could not establish txn type

but do not know what to do...

Thanks for any help
Dieter