Trying USB devices in Win7 VM blanks out VM settings?

[WmGBennett]

I'm having a strange error that I can't find anything about on the forum. I'm running Windows 7 (32bit) as the guest, in a Mac OSX Mavericks (10.9.2) host, under virtualbox 4.2.24. What happens is whenever I try to do anything involving USB devices - even just hovering on the usb devices sub-menu - virtualbox seems to go haywire in the following ways:
a) The settings window comes up blank, with just the 'cancel' and 'ok' buttons (and clicking cancel doesn't make it go away)\
b) shutting down the VM doesn't make it register as powered-off (it still reads as 'running')
c) the 'about virtualbox' pane shows 'r0' as the version number
d) all info about the current session seems to get blanked out

If I shut down the VM without trying to use a USB thing, it shuts down normally. If I quit virtualbox after it goes all wonky, it shows up as 'aborted' when I restart virtualbox.

First time I try to mount a USB thumb drive, I get this error:

Failed to attach the USB device USB DISK 2.0 [0100] to the virtual machine otwpl.

USB device 'USB DISK 2.0' with UUID {71a34486-083e-4f57-b421-d1e01b30df9b} is not in the right state for capturing (PhysDetached).

Result Code: NS_ERROR_INVALID_ARG (0x80070057)
Component: HostUSBDevice
Interface: IHostUSBDevice {173b4b44-d268-4334-a00d-b6521c9a740a}
Callee: IConsole {db7ab4ca-2a3f-4183-9243-c1208da92392}

Then, if I try again, I get this one:

Failed to attach the USB device Unknown device to the virtual machine .

Callee RC: NS_ERROR_CALL_FAILED (0x800706BE)

See screenshots of the weirdness below. Behaviour inside the VM seems to stay pretty normal.

Settings menu has disappeared!

Screen Shot 2014-03-17 at 9.08.03 AM.png (63.26 KiB) Viewed 1223 times

Screen Shot 2014-03-17 at 11.52.34 AM.png (13.69 KiB) Viewed 1223 times

Screen Shot 2014-03-17 at 11.59.32 AM.png (48.77 KiB) Viewed 1223 times

What I've tried so far:
1) Uninstalling and reinstalling virtualbox (most recent version), twice
2) Going back to version 4.2

It looks like these have fixed similar-ish problems for other people, but no such luck here. Can anyone suggest other ideas?

[socratis]

Do you have another application that uses the Qt4 toolkit?

[rpmurray]

I don't know about the USB problem, but I've seen the issue where a dialog box comes up without any text.

Try running Font Book, selecting all the fonts and then Validate Font to see if you're having any font problems. If so then fix them.
Also, it wouldn't hurt to run Disk Utility and do a Repair Disk Permissions just in case.

[ChipMcK]

Can anyone suggest other ideas?

Try VBoxSVC Blow out - V4.2.1 information inaccessible
Best of Luck