Actually it's very difficult to code your requirement.
Why,
take 1172003,I thought it's 11/7/2003.But actually it's 1/17/2003(only after reading your question detaily I came to know).Both are right.Though we can do some trick to seperate 1172003.But how the coding is goint identify whether it need to do 1/17/2003 or 11/7/2003?
why you are getting erroris because query analyzer dont know which date it should take.
Do a small test
select convert(datetime,'20030113')
and
select convert(datetime,'2003113')
from my point of view both represent the same date.How about QA,it need to take 2003/1/13 or 2003/11/3?
This is the reason you are getting error.If you can specify by adding zero before the days and months which is no more than 10.(instead of 1 input 01).You can help QA to know which date you really want.
Another thing you need to do is exchanging the year position with month and day position.(change 11132003 to 20031113)