Symptoms of a Virus

Biginning last Tuesday various machines within the building began experiencing trouble using MICROSOFT WORD and EXCEL. WORD displays a message that there is not enough memory to run spell check and EXCEL will not load a spreadsheet containing a macro. No changes have been made to the machines. If spellcheck is turned off, WORD will function but I can’t work around the EXCEL problem. It appears to be some sort of virus. Every machine has NORTON AV installed and up to date – I have made certain of this. Does anyone know of a new virus out there that would cause this problem or displays these symptoms?

Thank you for your help.