Using LabVIEW 2009 I can get the MathScript :
A = 1
for i = 1:1:10
A = A + 1
to compile just fine. After upgrading to 2009 SP1 (and also after applying the f3 patch and then upgrading to SP1) the same MathScript no longer compiles, however the script
%for i = 1:1:10
will compile. To test this I create a new VI in whichever version of LabVIEW I'm using and write the script from fresh - not copying or pasting from a previous file version.
The same behaviour is replicated in the built-in example "Mathscript Fractal.vi" - it only compiles for me when the for loop is commented out.
I've tried the steps suggested in http://digital.ni.com/public.nsf/allkb/DD220B71245A391E86257720007E1FE8. I don't detect any corrupt instantiations using the provided executable.
Any suggestions welcome...
 example in http://zone.ni.com/reference/en-XX/help/373123B-01/lvtextmath/msfunc_for/
You mentioned upgrading LabVIEW 2009 to 2009SP1 but did you also upgrade MathScript to 2009SP1? This is a common cause for problems since MathScript 2009 is not compatible with LabVIEW 2009SP1.