** VERSIONS OF GRID BELOW r1356 ARE NOT COMPATIBLE WITH WOW 4.0. UPDATE GRID BEFORE REPORTING ERRORS! **

What version of Grid are you using?
r1379

What version (and language) of WoW are you using?
enGB, 4.0.1

What were you doing when the problem occured?
Um, nothing. The error popped up when I still was on the loginscreen.

What happened? What did you expect to happen instead?
An error-free loading? :)

Do you have an error log of what happened?
Yes, here it is:

1x Grid-1.40000.r1379\GridRange.lua:79 attempt to call method 'SetSpellBookItem' (a nil value)
Grid-1.40000.r1379\GridRange.lua:97 in function <Grid\GridRange.lua:94
(tail call): ?:
<in C code>: ?
<string>:"safecall Dispatcher[1]":9: in function <[string "safecall Dispatcher[1]"]:5>
(tail call): ?:
AceAddon-3.0-5 (Ace3):539: in function <Ace3\AceAddon-3.0\AceAddon-3.0.lua:532
(tail call): ?:
(tail call): ?:
Grid-1.40000.r1379\GridCore.lua:266 in function `EnableModules'
Grid-1.40000.r1379\GridCore.lua:198 in function <Grid\GridCore.lua:195
(tail call): ?:
<in C code>: ?
<string>:"safecall Dispatcher[1]":9: in function <[string "safecall Dispatcher[1]"]:5>
(tail call): ?:
AceAddon-3.0-5 (Ace3):539: in function `EnableAddon'
AceAddon-3.0-5 (Ace3):629: in function <Ace3\AceAddon-3.0\AceAddon-3.0.lua:615
<in C code>: in function `LoadAddOn'
Interface\FrameXML\UIParent.lua:242 in function `UIParentLoadAddOn':
Interface\FrameXML\UIParent.lua:265 in function `CombatLog_LoadUI':
Interface\FrameXML\UIParent.lua:519 in function <Interface\FrameXML\UIParent.lua:492

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Does the problem still happen when you disable all addons (including Grid plugins) except for Grid?
Honestly I didn't tried that. But since I get the error without actively using Grid, I doubt it'll help.

Please provide any additional information below.

Please check on your ticket daily. If a ticket is waiting on a response from you for more than 7 days, I will assume that you have fixed the problem yourself and have abandoned the ticket.