i'm using the newest form of TMPGEnc and it starts to encode good, but then stops and give me that error of illegal floating decimal. (after I finally got past the common error of unsupported file! by raising the priority level in enviro setting) I'm doing everything right the site says in the setting and load features. hell, if you use the wizard it does everything (ntsc, aspect ratio to full screen keep aspect, 16X9, etc) I"ve done this before with success last year, so i'm not a newbie, maybe it's the version I have?
Make sure you have the latest version (2.510) and try encoding in Safe Mode, if it works, then go back to Normal, and make sure all other applications are closed up.
In Windows98/2000 and XP, when you boot up, you can press F8, and select Safe Mode, this loads Windows with minimum drivers (and 16 color display), this is best for testing software.