I've had this problem. If you ignore it, and just let the program complete, or indeed if it has frozen, shut it down, you can still save your work. The .vob files will be intact, so you just delete everything else and use IfoEdit to make new .ifo and .bup files. Done it dozens of times.
That said, I've never had that problem so far with 7.6 and it was happening all the time with 7.2 on the same install of XP. Don't know how related it may be to your virus as no such virus has been detected here by AVG.