To anyone with the error 0x3 I might have a solution. I found these while searching for a bit.
TOGETHER these two things could help, just try it.

Server Maintenance From 6pm PDT To 11:00pm PDT July 31st. Grand Chase Online sayed. I suggest playing it 2 hours after maintenance. I played the old versions before, and it sucks cause after each maintenance, you need to wait for the loading.

'i know a sollution to your problem,first on grand chase click properties>>> Compatability Tab>>>>
you will see a compatability mode....check the small white box beside it the>>>>> click the arrow

Grand Chase Patch Download Error

down beside te box then select 'Windows NT 4.0 (Service Pack)....Then Apply'
'go Start>>>Control Panel >>> Network Connection>>>go Local Area Connection >>>click

Grand Chase Patch Download Unavailable

Properties>>> select Internet Protocol >>> click Properties >>>
Preferred DNS server : 208 67 222 222

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Alternate DNS server :

Grand Chase Error Patch Download Unavailable

208 67 220 220 '
(FOR VISTA/WIN 7 USERS)
>>>>Network sharing Center>>>>>>Change Adapter Settings>>>>>>Current Network Connection>>>>>Properties>>>>>>IPV4>>>>>>Change DNS