I have burned DVD+Rs with Gear, Nero, Imgburn, Roxio's EasyMediaCreator and the Plextor PX-810SA with no problem. I also tried a Verbatim DVD+R DL with DVDA 4.5a and it burned through the lead-in but hung at 8% of the burn. I have reported the problem to support.
I installed DVD Architect 3.0c (build 133) and created the same project then burned a Sony DVD+R with the Plextor PX-810SA and it burned with no errors and no hang on lead-in/out and the DVD played fine!
I also tried DVD Architect 4.0b (Build 166) which failed the same as DVDA4.5a.
It sure looks like the problem with the plextor was introduced with changes made in DVDA4X from DVDA3.0c.