Same here on Win7 x64 - takes a lot of time to start and after that an error message shows up: Launch4j - An error occurred while starting the application.
Here is my log but nothing obvious:
CmdLine: D:\Projects\Arduino\arduino.exe --l4j-debug
Working dir: D:\Projects\Arduino.
Bundled JRE: java
Check launcher: D:\Projects\Arduino\java\bin\javaw.exe (OK)
Add classpath: lib\pde.jar
Add classpath: lib\core.jar
Add classpath: lib\jna.jar
Add classpath: lib\ecj.jar
Add classpath: lib\RXTXcomm.jar
Launcher args: -Xms128m -Xmx128m -classpath "lib;D:\Projects\Arduino\java\lib\tools.jar;lib\pde.jar;lib\core.jar;lib\jna.jar;lib\ecj.jar;lib\RXTXcomm.jar" processing.app.Base
Args length: 159/32768 chars
[UPDATE1]I tried every suggestion above and in the other posts. Installing 1.5.2 does not fix it either.
Is there a way to enable the log in more verbose mode where I can actually see what the problem is?
So when I delete the \Documents\Arduino\libraries folder it runs once after that and it runs ok. If I close and open that IDE after that it comes bask to the old problem and I have to delete the folder again so it can work .Very weird!
[SOLUTION] I had Sierra Wireless Application Interface on Com4. I was not using it, it's just a driver for the Sierra Wireless I had before. After disabling it it all works smoothly. So any Com ports can cause some issues, in my case was this one.