modify column from VARCHAR to LONG

Hi,

I need to modify one column in a table from varchar to LONG.

In the archive I found the workaround:
1.) rename table to temp_table
2.) create new table with LONG inside
3.) transfer data from temp_table to new one via
    insert into new_table (col1, col2,..) select col1,col2,... from
temp_table

I want to do this in SQL-Studio, but step 3.) fails with error:

"General error;-7032 POS(295) SQL statement not allowed for column of data
type LONG"

I'm using version 7.0.3.34. Can somebody tell me how to finish this task ??

thanks in advance ..:GERD:..