Create Table, Insert Into

I was having an issue summing up the clientcred.defmonthlypayment column on a user by user basis when I was joining it with another table to get only "active" objects. It would return exponentially large numbers when joined to the other table. So I was trying to drop it into a temp table so i could query against it to get the results I needed. But it keeps telling me that 'null' values arent allowed in the 'clientid' column when I instucted it to put the results into another column and to allow 'null' values in that column.

error message at the bottom

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CREATE TABLE #accts (
clientid int primary key,
clientid1 varchar(6)null,
monthlyacctpayment varchar(10)null,
grp1 int null,
clientid2 varchar(6)null,
monthlyacctfees varchar(10)null,
grp2 int null
)

INSERT into #accts
(clientid1,monthlyacctpayment,grp1)
SELECT distinct clientcred.clientid as 'clientid1',
CAST(sum(clientcred.defmonthlypayment) as varchar)'monthlyacctpayment',
GROUPING(clientcred.clientid) 'grp1'
FROM clientcred
GROUP BY clientcred.clientid WITH ROLLUP


INSERT into #accts
(clientid2,monthlyacctfees,grp2)
SELECT clients.clientid as 'clientid2',
CAST(sum(clients.monthlyacctfee) as varchar)'monthlyacctfees',
GROUPING(clients.clientid) 'grp2'
FROM clients
GROUP BY clients.clientid WITH ROLLUP


Select clients.clientid,monthlyacctfees,monthlyacctpayment from #accts,clients
where clients.active='-1' and clients.clientid=#accts.clientid

drop table #accts

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Results

Server: Msg 515, Level 16, State 2, Line 14
Cannot insert the value NULL into column 'clientid', table 'tempdb.dbo.#accts______________________________________________________________________________________________________________00000001CFA5'; column does not allow nulls. INSERT fails.
The statement has been terminated.
Server: Msg 515, Level 16, State 2, Line 23
Cannot insert the value NULL into column 'clientid', table 'tempdb.dbo.#accts______________________________________________________________________________________________________________00000001CFA5'; column does not allow nulls. INSERT fails.
The statement has been terminated.


Why is it trying to drop the requested info into the clients column when I state that it should be dropped into the specified column?

I apologize for any statements or references that are wrong now but thats why I posted in the 'new to SQL Server' section. Thanks everyone