MOTM

Hi all,
 I finally got around to doing the unity gain mod as described on Scott 
Juskiw's site:

http://www.tellun.com/motm/mods/motm830/motm830.html

 After replacing the resistors, I spent a good hour+ troubleshooting an 
oscillation that was being output from the OUT1 jack. I didn't find any solder 
splashes, or anything else physically wrong, so I reinstalled the original 
resistor at R18 (100K). The oscillation problem went away, but so did unity gain 
increase from inputs 4, 5, and 6 to OUT1. 

 So, any ideas what might be the cause of this problem? Do I have a bad 
OP285, or is will changing the value of C1 help?

 Thanks for any ideas,
 Andrew Sanchez