SONAR.Heuristic.130 question

I was installing a new program when I got the notice from Norton that the operation was being cancelled because the program contained the SONAR.Heuristic.130 virus/trojan.  The people I'm purchasing the program from say it's because their program is not widely used and is not in Norton's database and therefore is suspect.  They suggest that I disable Norton while I install it - something I'm not really thrilled about doing.  Any thoughts?  Is their claim that the notice is due to the program being unknown valid?