SUM() function behave differently than Sum operator.
1) write in cellA1=1
2) write in cellA2=2
3) write in cellA3=SUM(A1:A2), got results 3
4) write in cellA4=A1+A2, got results 3
5) modify cellA1 to '-', '/', ' ' or '\' (not a number)
in cellA3 the value become 2 as expected
in cellA4 the value become #VALUE!
Note: with OpenOffice 3.3.0 the value in cellA4 become 2 as expected,
this generate an incompatibility to existent .ods electronic sheet,
as #VALUE! propagate to next formulas
It is the same behavior as in MS Office. It was changed in LibO 3.4.0
the bug is about compatibility with previous .ods calc sheet and opensource applications. All previous native .ods file that use this behavior require fixes for this LO modifications