ubuntu 12.10 with firefox 17.0

firefox is now suddenly not starting any more ?

(since I tried something with virtualbox and win7 firefox seems to be raided somehow ? - then after next boot virtualbox with win7 did not work any more and had message like here:

Premature end of data in tag VirtualBox line 8.
Location: '/home/$user/VirtualBox VMs/V12/V12.vbox', line 86 (8), column 2.
/home/vbox/vbox-4.2.4/src/VBox/Main/src-server/MachineImpl.cpp[724] (nsresult Machine::registeredInit()).
Fehlercode:
NS_ERROR_FAILURE (0x80004005)
Komponente:
Machine
Interface:
IMachine {22781af3-1c96-4126-9edf-67a020e0e858}

)

this happened all - after win7 made an update and virtual hard-disk with size of normally 25 Gibi exceeded to 26.8 Gibi

I plugged (when I created virtualbox with win7) usb-hard-disk with 500 Gibi, but somehow win7 was not installed on disk with 500 Gibi - instead only virtual-harddisk with default 25 Gibi was created - and smaller harddisk with maximum of 120 Gibi was restless stuffed out. This created then the problem with "raided" firefox and firefox cannot start any more. After I delelted virtualbox with win7 - there are 12 Gibi free space back on the smaller harddisk - but firefox remains after reboot out-of-function and does not start.