Got this today.. i'm using v2.0.1 .. i think the error appeared because i rushed to open the oQ interface right after login instead of waiting ~20 sec as i usually do:

Date: 2014-09-13 12:42:42
ID: 1
Error occured in: Global
Count: 1
Message: ..\AddOns\oqueue\oqueue.lua line 21418:
attempt to perform arithmetic on field '?' (a nil value)
Debug:
[C]: ?
oqueue\oqueue.lua:21418: decode_mime64_digits()
oqueue\oqueue_tooltips.lua:819: pm_tooltip_get_xpbar()
oqueue\oqueue_tooltips.lua:1027: pm_tooltip_set()
oqueue\oqueue.lua:9520: on_premade_item_enter()
oqueue\oqueue.lua:10296:
oqueue\oqueue.lua:10296
Locals:

P.S.

i've seen other errors in decode_mime64_digits() on the forums too:

https://solidice.com/forums/1/topic/oqueue-199-lua-errors

maybe take a closer look at that function and add an initialization check?