If problems are found on any of these aircraft they still may fly though under a reduced flight envelope so as not to strain and fatigue the horizontal stab. It will take Boeing about 8 days to repair each horizontal stab if problems are found. For the production aircraft this won't affect their delivery since these airplanes are not flying and can be easily repaired before delivery. Boeing will focus on fixing any of the issues with ZA001 through ZA006 as these are the test flight airplanes and getting them fixed and returned to flight test will be a priority.
I don't think there will be much effect on the flight test program and their is some margin in the test flight schedule. Boeing main issue to discover who this problem got past quality control and develop methodologies to make sure manufacturing errors like this don't occur. The issue also is why Alenia is having so many manufacturing issues with their product that they deliver to Boeing.
Boeing also says that they're going to go ahead with plans to bring ZA003 to Farnborough next month though they have not finalized those plans as of yet. If they do bring it it will go a log way to repairing Boeing's image vis a vis the 787.
Boeing also announced a production related change. There will production slow down in September due to resequencing of part deliveries into Everett for final assembly. This is due to customers taking different delivery dates. This will allow Boeing suppliers to catch up and to improve the supply chain health. Boeing is planning to implement the resequencing after airplane 27 (ZA178, LN 27) is delivered. Boeing indicated that the resequencing of deliveries shouldn't impact deliveries in 2010 and 2011 to customers.
In some other 787 news, Vietnam Airlines announced that they are switching their order from the 787-8 to the 787-9. The reason being is that the airline believes that the -9 will be a better performer than the -8. This came on the heels of Boeing announcing 3 more 787s orders from an unidentified customer.
Lastly, ZA006 which will be the last test flight 787 to take flight won't fly on July 13th as previously reported but now has been pushed back to July 26th. This is before the horizontal stab issue came to light. I don't know if the new problem will further push back ZA006's first flight or not but this airplane has to be inspected first.
Dominic Gates : Boeing Halts Flights for 787 Inspection
Dominic Gates : Dreamliner Chief Says Production Will Slow In September
Flightblogger : Gaps in horizontal stabilizer prompt another Alenia 787 quality issue
Flightblogger : Boeing plans additional re-sequencing of 787 parts deliveries
Flightblogger : Boeing starts 787 horizontal stabiliser inspections
Guy Norris : Boeing 787 Test Flights Halted
Aubrey Cohen : Boeing finds glitch in 787 horizontal stabilizers
Aubrey Cohen : Boeing inspecting 787s, plans to slow production in September
Flightglobal : Vietnam Airlines switches 787 order to -9s
Bloomberg : Boeing Says 787s May Need New Tail Parts After Inspections
Randy Tinseth : 787 inspections prioritized
Geoffrey Thomas : Boeing to bring 787 to Farnborough, happy with flight testing progress