Tilde symbols are driving me mad! Please help!!

Hi everyone,

I am experiencing a problem where the Tilde symbol is being added to file names after I have 'saved for web' in photoshop. Regular names suddenly go to all caps with a tilde symbol added in the middle.

For example:
'File-name.jpg' suddenly becomes some like 'FILE~NAME.JPG'

This is particularly problematic when I then need to use these images online.

Please help, very simple jobs are taking a very long time!!!

Thank you in advance