Powerpivot error modify calculated measures that contains ";" by PaoloLec

I have a problem with PowerPivot.
When I try to modify a calculated measures that contains ";" appear the error "the expression is not valid or appears to be incomplete. Please review and correct the expression. The syntax for ";" is incorrect."
If I put a space after all and press enter it works fine (also if I replace ";" with "," and then press the checkmark of the formula).
The problem is appear magically and now all new excel have the same problem.
The problem is on more different computer.

Detail:
SQL 2012 PowerPivot for Excel v.11.0.2100.60
Language:
Format: italian
Location: Italy
Keyboard and language: italian
Display Language: English

Excel v14.0.6023.1000 64 bit
Language in Excel options: Italiano
PowerPivot Language Setting: italiano.