vbulletin does attachments via a normal http input prompt the same way our normal upload process works.
The issues with the flash uploader where with it not working with flash 10. Because this code is written by someone else we had to wait for them to provide working code. This is the main reason why we included an on off switch in admin for this option. Photopost Pro 6.21 and vbGallery 2.5 beta both contain flash uploaders which work with flash 10 now.