I made your file comma delimited but all the rest is the same. Try this solution:

CREATE CURSOR xx(pk i, pid C(4), lineid C(3), revnum i, origrev i, rectype c(1))
APPEND FROM xx.txt DELIMITED

SELECT pk, pid, lineid, revnum, origrev, rectype ;
	FROM xx WHERE rectype = "A" ;
UNION ;
SELECT pk, pid, lineid, MAX(revnum) revnum, origrev, rectype ;
 FROM xx WHERE rectype = "I" AND lineid IN ;
 (SELECT lineid FROM xx WHERE rectype ="A") ;
  GROUP BY lineid INTO CURSOR cfini

============

>I have a header/lineitem problem.
>
>The header table has the following fields:

>RecordId   DocId    RevNum
>------------------------------------
>       1    0001         3
>

>
>The LineItems has:
>

>RecordId   ParentId   LineId    RevNum   OrigRev  RecType
>------------------------------------------------------------
>    1          0001      123         1       999        I
>    2          0001      123         2       999        I
>    3          0001      123         3       999        A
>    4          0001      890         1       999        I
>    5          0001      890         2       999        A
>
>

>
>I need to pull all active record (RecType = "A") and the record
>which was active just prior to the currently active record.
>
>So in the example above, if I wanted to see the active line item
>and previous record for line item 123, I would get the line items
>record Id's with 3 and 2.
>
>Any ideas?