p.s. in script i using loopand "go to record" function with "end on last record"
Can you post a copy of your script?
Filemaker 10 interacts with a found set just the same as filemaker 5.
One factor that can be an issue is if you have added a script trigger that is firing due to some action that takes place while your script is attempting to loop through the records.
If you have a Go To Related Record step, it can leave you with a different found set than you expect under certain circumstances and this is different from what would happen in v5.
Go To Related Records is a very useful tool, but which is very poorly documented. To learn more about GTRR, click the following link:
The Complete Go To Related Record
The looping in that script will work exactly the same in 5 and 10. Check your found set at the beginning of this script. Check your layout--are you on the layout you should be? Does this layout refer to the table occurrence it should? (Different table occurrences with the same data source table will have different found sets, current records and sort orders.)