Hi Phani,
You are welcome. My offer is to repeat the same issue you face in my system and below is what i've tested in my ECC 6.0 environment.
Without Posting Block Checked in Billing Doc Config.
Creation of Billing Document WOPB with account determination error. Posting Status is reflecting as "Error in accounting interface" before saving (VF01) and "B Posting Document Not Created (Account determ. Error" after saving(VF03). This is another inconsistency with your system.
With Posting Block Checked in Billing
Creation of Billing Doc WPB with account determination error. Posting status is reflected as "A Billing document blocked for forwarding to FI" both before and after saving.
Now in VFX3, Billing Doc WPB is reflected as accounting block, while billing doc WOPB is reflected as "acct determin. error".
What's really interesting here is the difference in Posting Status in VF01 between your system and mine. With posting block checked, my billing block is reflected as "A Billing document blocked for forwarding to FI" instead of what you have observed "Account Determination Error". This is the inconsistency that I've noticed.
Thanks
Leonard