Can anyone tell me what this means? I've burned a few movies and this is the first time it happened.

1/16/2007 8:40:31 PM info ********** Report session closed ***********
1/16/2007 8:32:35 PM info Media removed. Burning layer not ready to write
1/16/2007 8:32:20 PM error Exception encountered in read thread [Access violation at address 7C917A8C in module 'ntdll.dll'. Read of address 5C34452D]
1/16/2007 8:32:19 PM error Write error at 619648 (16) - Code 06 28 00 [Unit attention, Not ready to ready change, medium may havbe changed]
1/16/2007 7:53:53 PM info Lead-in burning time (mS) 13684
1/16/2007 7:53:40 PM info Write started 2148080 sectors to write
1/16/2007 7:53:40 PM info Init success: DVD-R packet writing
1/16/2007 7:53:39 PM info Writing speed requested x4.0, effective x4.0
1/16/2007 7:53:36 PM info Available write speed: 16x, 12x, 8x, 4x
1/16/2007 7:53:36 PM info Media ID: RITEKF1
1/16/2007 7:53:36 PM info Scanned files #12, folder #2 - total size 4398139392 b. (4.1 Gb.)
1/16/2007 7:53:36 PM info Inserted media type : DVD-R
1/16/2007 7:53:36 PM info Write started
1/16/2007 7:53:35 PM info --------------Encoding end--------------