@Thansen_DK it seems like an issue with board autodetection. On windows we use a program called listComPorts.exe (credits to todbot).
Can you run that program directly? It's located at YOUR_IDE_FOLDER\hardware\tools
No, running listComPorts.exe generates the error
Is the popup blocking the tools menu from working correctly?
Yes it does.
What's wierd is that on an other machine also running Win8 Pro 32 bit. I could start Arduino 1.5.4 without the error, but my antivirus (Bitdefender Antivirus Pro 2013) detected listComPorts.exe as potentially malicious and blocked it, maybe thats why i don't get an error on this machine.