trouble uploading on ubuntu 12.04

Development Tools IDE 1.x
8

I think the Arduino IDE, or maybe one of the libraries it is using, is creating the lock after I start the IDE and subsequently prevents the IDE from communicating with the serial port.

Before running the IDE, I tried the following:

$ ls /var/lock
LCK..ttyACM0  multiload-icons-PwgnzL  whoopsie
$ sudo rm /var/lock/LCK..ttyACM0 
[sudo] password for user:

Then I run the arduino IDE and try to upload Blink:

$ ./arduino 
Experimental:  JNI_OnLoad called.
Stable Library
=========================================
Native lib Version = RXTX-2.1-7
Java lib Version   = RXTX-2.1-7
Binary sketch size: 1,084 bytes (of a 32,256 byte maximum)
processing.app.SerialException: Error opening serial port '/dev/ttyACM0'.
	at processing.app.Serial.<init>(Serial.java:178)
	at processing.app.Serial.<init>(Serial.java:77)
	at processing.app.debug.Uploader.flushSerialBuffer(Uploader.java:77)
	at processing.app.debug.AvrdudeUploader.uploadViaBootloader(AvrdudeUploader.java:172)
	at processing.app.debug.AvrdudeUploader.uploadUsingPreferences(AvrdudeUploader.java:67)
	at processing.app.Sketch.upload(Sketch.java:1706)
	at processing.app.Sketch.exportApplet(Sketch.java:1662)
	at processing.app.Sketch.exportApplet(Sketch.java:1634)
	at processing.app.Editor$DefaultExportHandler.run(Editor.java:2346)
	at java.lang.Thread.run(Thread.java:679)
Caused by: gnu.io.UnsupportedCommOperationException: Invalid Parameter
	at gnu.io.RXTXPort.setSerialPortParams(RXTXPort.java:171)
	at processing.app.Serial.<init>(Serial.java:163)
	... 9 more
processing.app.debug.RunnerException: Error opening serial port '/dev/ttyACM0'.
	at processing.app.debug.Uploader.flushSerialBuffer(Uploader.java:101)
	at processing.app.debug.AvrdudeUploader.uploadViaBootloader(AvrdudeUploader.java:172)
	at processing.app.debug.AvrdudeUploader.uploadUsingPreferences(AvrdudeUploader.java:67)
	at processing.app.Sketch.upload(Sketch.java:1706)
	at processing.app.Sketch.exportApplet(Sketch.java:1662)
	at processing.app.Sketch.exportApplet(Sketch.java:1634)
	at processing.app.Editor$DefaultExportHandler.run(Editor.java:2346)
	at java.lang.Thread.run(Thread.java:679)