I'm getting this same error in the latest wallet version 2.9.0
I guess this bug will never be fixed.
This is an old thread and you are just bring this back alive..
Let me know your bitcoin address to know if you bitcoin address are still holding some bitcoins..
And also try to check the preferences and check the good fee here
https://bitcoinfees.21.co/ or set it into 0.0014 and try to send your coins to other bitcoin address..
If not working you can also try this one goto to addresses and look for the address with bitcoin and right click and choose send from and try to send it to your new bitcoin address you own..