Wow has this been a hot topic for a long time.
And sorry for not posting in my original post but there are many posts with similar problems and so on.
This is a real eye opener for me.
Quickly to re-cap the story:
I had some "Freetronics" arduinos and they worked.
One day I bought a new one and it was getting these sync errors. avrdude not in sync and all those kind of problems.
I was pulling my hair out over it - and about that time other people started getting the same problem.
I tried different IDEs and all that, but no luck.
I still had my laptop and the "original" card. They worked. Other combinations of cards and computers didn't work.
Today I wanted to update/fix up the sketch in my working arduino from my laptop.
Now, at this point, the laptop is using the same version as worked last time, and the card... Well, it is the same.
I tried to flash it and: (Drum roll.....) Not in sync.
So there is something going on which is really strange.
The laptop has been updated from windows a few times, but it isn't on the net that often.
So what I may do next time I get a chance is try one of the newer cards with the laptop and work from there.
I hope this is helpful to anyone who still had this problem.
Don't give up. I didn't and finally did get the desktop and other cards working again.