I've seen a lot of confusion about the scope and lifetime of temporaray tables.
While i think that ##global temp tables are clear, #local temp tables are a different story.
They seen to sometimes work and sometimes not, especially when used with dynamic sql.

So what is the problem?
Mostly basic misunderstanding.
So because i'm such a nice guy, i'll try to elaborate a bit about "them darn #temps". :)

BOL clearly states:

Local temporary tables are visible only in the current session... ... Temporary tables are automatically dropped when they go out of scope, unless explicitly dropped using DROP TABLE

-- 1st example
-- this fails
use northwind
exec('select top 5 orderId, customerId into #temp from orders; select * from #temp')
select * from #temp 
drop table #temp 

-- 2nd example
-- this works
use northwind
select top 5 orderId, customerId into #temp from orders
exec('select * from #temp')
select * from #temp 
drop table #temp 

-- 3rd example
-- this works
use northwind
create table #temp
(
    orderId int,
    customerId varchar(5)
)
insert into #temp
select    top 5 orderId, customerId
from    orders
exec ('select * from #temp')
select * from #temp
drop table #temp