Uploading Woes

All of a sudden I am getting a whole heap of error messages when trying to upload sketches to Arduino.

Annoyingly I can’t copy them here but I’ll type some of them out:

Error inside Serial.()
gnu.io.PortinUseException: Unknown Application


at processing.app.Serial.(Serial.java:127)
at processing.app.Serial.(Serial.java:72)
at processing.app.Uploader.uisp(Uploader.java:146)

and quite alot more error messages until finally

Error: permission denied

→ /dev/com9

After booting up my pc I can upload a sketch but to upload a second sketch returns these messages.

Any ideas?