We had a client that recently received an overflow error. After running through the suggested methods from Microsoft we still couldn't get past the error.
Then we noticed that the column width for the account description was set to 15 characters. The user thought that if they shrunk the column it would just copy off the field. This is not the case. It could be a bug that it throws an error or just a design flaw.
How we found the right size to set the description to is run the following script:
select max(len(ACTDESCR)) from GL00100
The result is the account number witht the longest length. We then set the width to that value and the problem went away.
The alternative is to set the width to the maximum field size of 30 or set no width at all.