I just tested your code, and it worked just fine.
Could you create upload a testcase somewhere?
-- F.
That code's missing a "+" before the last slice retrieval:
"|" store.getTiddlerSlice(tiddler.title,"Authentication")
I've made a few more, minor changes:
---------------
<<forEachTiddler
where 'tiddler.tags.contains("LoginId")'
sortBy 'tiddler.title.toLowerCase()'
write '"|[[" + tiddler.title + "]]|"
+ store.getTiddlerSlice(tiddler.title, "Company") + "|"
+ store.getTiddlerSlice(tiddler.title, "Domain") + "|"
+ store.getTiddlerSlice(tiddler.title, "Authentication")+"|\n"'
begin '"|>|>|>|!Current Login Definitions|h\n"
+ "|!Definition|!Company|!Domain|!AuthenticationId|h\n"'
>>
---------------
(cf. http://tiddlywiki.pastebin.com/f22567f9e)
HTH.
-- F.