I did a reinstall, and it's still not loading. The error is a little different, but probably the same problem. I'm going to submit a bug report on Archlinux, since it may be a missing dependency or something.
Code:
calibre 2.68 embedded-python: False is64bit: True
Linux-4.7.5-1-ARCH-x86_64-with-glibc2.2.5 Linux ('64bit', '')
('Linux', '4.7.5-1-ARCH', '#1 SMP PREEMPT Sat Sep 24 13:04:22 CEST 2016')
Python 2.7.12
Linux: ('', '', '')
devicePixelRatio: 1.0
logicalDpi: inf x inf
physicalDpi: -151097187.422 x -268699924.43
QWidget::setMinimumSize: (/Wizard) Negative sizes (-402653024,0) are not possible
QWidget::setMinimumSize: (/Wizard) Negative sizes (0,-626349394) are not possible
QWidget::setMaximumSize: (/Wizard) Negative sizes (-402128897,16777215) are not possible
QWidget::setMaximumSize: (/Wizard) Negative sizes (0,-609572179) are not possible
QWidget::setMinimumSize: (/QWidget) Negative sizes (-492131479,55) are not possible
QXcbConnection: XCB error: 2 (BadValue), sequence: 403, resource id: 0, major code: 1 (CreateWindow), minor code: 0
QXcbConnection: XCB error: 3 (BadWindow), sequence: 404, resource id: 12582917, major code: 2 (ChangeWindowAttributes), minor code: 0
QXcbConnection: XCB error: 3 (BadWindow), sequence: 405, resource id: 12582917, major code: 18 (ChangeProperty), minor code: 0
QXcbConnection: XCB error: 3 (BadWindow), sequence: 406, resource id: 12582917, major code: 18 (ChangeProperty), minor code: 0
QXcbConnection: XCB error: 3 (BadWindow), sequence: 407, resource id: 12582917, major code: 18 (ChangeProperty), minor code: 0
QXcbConnection: XCB error: 3 (BadWindow), sequence: 409, resource id: 12582917, major code: 18 (ChangeProperty), minor code: 0
QXcbConnection: XCB error: 3 (BadWindow), sequence: 410, resource id: 12582917, major code: 18 (ChangeProperty), minor code: 0
QXcbConnection: XCB error: 3 (BadWindow), sequence: 411, resource id: 12582917, major code: 18 (ChangeProperty), minor code: 0
QXcbConnection: XCB error: 3 (BadWindow), sequence: 414, resource id: 12582917, major code: 18 (ChangeProperty), minor code: 0
QXcbConnection: XCB error: 3 (BadWindow), sequence: 418, resource id: 12582917, major code: 2 (ChangeWindowAttributes), minor code: 0
QXcbConnection: XCB error: 3 (BadWindow), sequence: 419, resource id: 12582917, major code: 18 (ChangeProperty), minor code: 0
QXcbConnection: XCB error: 3 (BadWindow), sequence: 422, resource id: 12582917, major code: 18 (ChangeProperty), minor code: 0