Hi,
[http://eu.wowarmory.com/guild-info.xml?r=%7B%7Burlencode:%7B%7B%7Bserver%7D%... {{{name}}} Armory] }}
You first have to find out if the {{{name}}} actually contains the leading and trailing space. If it does, then the urlencode is your problem, otherwise the problem lies in passing leading/trailing spaces to named template parameters.
The following did not work?:
{{Guildbox | name =  M A  | server = Bleeding Hollow | location = US | image = | leader = Deadhead {{RaceIcon|Human|Male|Small}}{{ClassIcon|Priest|Small}} | level = 1-80 | type = PvP | faction = Alliance | accounts = 256 | web = http://www.ma-wow.com/ }}