I just got the 6600. I did purchase the extra bobbin case and I really like it for fmq. I never have to adjust anything when I use it. I was never able to fmq before and it works great for me.

I always use a bobbin spacer. It cuts down on the chatter you hear from the bobbin case. I also have the other bobbin case, not sure if it makes a difference or not.

The special bobbin case seems to work really well for me. I just don't have problems (eye-lashes) when i use it. I believe one could tweak the tension for me the expense of having a separate bobbin case was worth it.

I have the 6600 and this happened to me as well. I joined the yahoo Janome group and was told to oil the wick. I did this and it took care of this problem.

I have the 6600 and love it. My thread comes out of the tension gage every once in a while and I shut the machine off and on, re-thread the top and reset the bobbin. I would take it back to the dealer and have them check the bobbin case. You don't want to have issues later and you no longer are under warrenty.

There is a common quirk in this wonderful machine. The thread will sometimes come out of the take up lever. This makes a noise and a mess on the back. Join that wonderful yahoo group and you will learn LOTS.

So what is the solution that has been figured out?

The biggest problem I had when I bought my Janome 6600 three years ago was the bobbin. Never could get good tension. Trips back to the dealer didn't help as they couldn't find any problem. It turned out that I was not always inserting the bobbin in counter-clockwise. Also it seems important to use Janome bobbins since they are slightly different. As wvdek said they are not concave like other bobbins. Plus one dealer told me that the Janome does not like to sew when the bobbin thread gets low. I've become a believer on that tip, too. If you get a bouncing sound when sewing, stop because there is something wrong. I always rethread and check the bobbin when there are problems and agree that turning the machine off and on is good to do. Just like any computer, they reset themselves.

I was fmq yesterday w/ my Janome 6600 and had that problem a time or two. I found that it resolved when I kept firm tension on the top and bottom threads as I was starting out (making anchoring stitches). I have not had a problem since. Also, I use my old metal Babylock in my Janome and have not had a problem in the 2 years I've had her. Make sure you insert the bobbin with the thread coming off the left side, looking like a "p".

As Feffertim pointed out, there is an oil wick hole under the bobbin case which dries out on
some machines causing the bobbin case to growl, rattle and literally jump out of place. No
where in the manual does it tell you to oil it there but I learned about it on the Janome
6500/6600 forum. My bobbin case rattled so badly that it would jump out of place and make
huge thread nests. My Janome dealer was no help and kept telling me it was operator error.
Not all machines seem to need this spot oiled regularly but mine certainly does.