Start with these links on the RIGHT SIDE of the Premiere Forum
How to ask a question http://forums.adobe.com/thread/416679
Premiere FAQS http://forums.adobe.com/thread/424418
Premiere Tutorials http://forums.adobe.com/thread/424009
PPro Wiki http://premierepro.wikia.com/wiki/Adobe_Premiere_Pro_Wiki
PPro Help http://help.adobe.com/en_US/PremierePro/4.0/index.html
A link with many ideas about computer setup http://forums.adobe.com/thread/436215?tstart=0
And even more hardware discussion http://forums.adobe.com/community/premiere/hardware_forum
Work through all of the steps (ideas) listed at http://ppro.wikia.com/wiki/Troubleshooting
If your problem isn't fixed after you follow all of the steps, report back with the DETAILS asked for in the questions at the end of the troubleshooting link
When something works one day, but not the next, then something has changed. The task is finding out what has changed.
Sometimes, it's something like an OS update killing a video, or audio driver (very common), and sometimes it's the addition of some program, that has VST's, especially "instrument" VST's. Sometimes, simple hardware additions can kill things.
Have you tried going to a previous System Restore Point, from back when things did work well? That would be the first thing that I would try.
Next course of action would be to do a Repair Installation of the Adobe programs, in case a .dll, or other file, was broken, or corrupted.
There was also a fairly recent thread on a user, who had attempted an FLV Export. That failed, and it seemed that the failure hosed something in PrPro. Not sure what that poster ended up doing, but think that they did solve the problem. You might want to Search this forum for that thread. I'd look for similar keywords, as appear in your title. I think that I commented on that thread, and believe that Harm Millaard, and Jeff Bellune might have, as well. If you are not having luck with just the keywords, maybe throw in People, and choose Harm, Jeff and finally me. Wish that I could recall that thread more clearly, but I think that there were some strong similarities.
Most of all, good luck,
It is hard to believe that there was a simple fix. I tried System Restore, but could not get a good Restore even after disabling the virus/firewall… However, I uninstalled 2 programs that were loaded between having a “working” and “nonworking” Export function on Pre Pro and restarted my computer. Everything is back to normal – all works. The 2 programs were the new version of Adobe Reader and Adobe Air. I don’t know why Adobe Air was installed yesterday?
Thanks for the help – I was sick at the possibility of reinstalling of CS4/Plugins, etcs
Adobe Air is one of those extremely annoying programs that ask to be updated
frequently. It annoys me so much I consider it almost VIRUS like. Its behavour in this regard is certainly unwanted!
My best efforts to get it to desist have failed.
I find that I always get great System Restores from Safe Mode. Not one has failed on any machine (he knocks wood, as he types).
Adobe Air possibly got installed with Adobe Media Player, though there could be other ways.
Most of all - good luck, and thanks for reporting,