FB 1.5.3.4870
XP Pro SP2

I have a mysterious failure in an SP when I check if a variable is
blank.

I get a "arithmetic exception, numeric overflow, or string truncation"
when I test for InternalMemo <> ''.

InternalMemo is VarChar(2000) and is filled from a memo field like this:
Select...<field list>
Coalesce(SubString(O.MEMO_INTERNAL From 1 For 1990),'')
into ... InternalMemo

Then later in the procedure I check to see if it contains something by:
if (InternalMemo <> '') then
...do something

But I get the error at the "If" test

Does this ring any bells with someone? I don't see what I am doing
wrong.

Rick