According to the Texas Secretary of State, both the Republicans and Democrats filed paperwork before the deadline and then filed amendments to the paperwork after their conventions.
If you look at the Texas official website. Both McCain and Obama are on the official ballot. Now Barr may sue and claim otherwise. But good luck with that in the Texas courts.
http://www.sos.state.tx.us/elections/candidates/general/2008gensbs.shtml
Barr is beyond an egotistical a-hole [IMO]...I'm so sure that McCain and Obama would be held to that deadline requirement even though they had not even been officially nominated by their parties...and McCain would have been on the ballot without a running mate as he had not chosen Sarah at that time.