avrdude: stk500_getsync(): not in sync: resp=0x44

A new error... After working fine for days, I now get the error "avrdude: stk500_getsync(): not in sync: resp=0x44" while flashing a sketch to the nano. Serial (via FTDI/USB) still working, flashing via ISP working.

Can someone tell me what the error tells me? Google could not help me and avrdude documentation also doesn't give a hint...

Remark: Oops, wrong forum, could some mod just remove it here? Thanks!

Google could not help me

You didn't look, then. That message, and it's causes, has been posted millions of times.

That message, and it's causes, has been posted millions of times.

As I'm not able to find any notice on that 0x44 response code, maybe you could just give me just one out of these 1 million links?
http://www.google.com/search?btnG=1&pws=0&q="resp%3D0x44"