Insert Exec cannot be nested

I had the following statement in my stored procedure

INSERT INTO #nextMtg EXECUTE proc_nextMtgList @estID,'', 0

I got the error 'Insert Exec cannot be nested...' and I realised there is another INSERT INTO..EXECUTE stmt in the same store procedure. So I changed my line of code to

INSERT INTO #upcomMtg
Select * from openrowset('SQLOLEDB','Server=<instance\servername>;UID=<uid>;PWD=<pwd>;database=<dbname>;Trusted_Connection=yes;','EXEC <dbname>.dbo.proc_nextMtgList 526,'''', 0') AS a

Now I am getting the error 'Invalid object name #rvmyMtg'
#rvmyMtg is a temp table created in the stored procedure proc_nextMtgList.

The stored procedure proc_nextMtgList is working correctly by itself. What could be causing the invalid object error?