While attempting to post an invoice in Order Entry a client received this message. After which the system basically froze up as she had to log off the PC and log back in and re-enter the invoice.

Error of 1001 “ToXLRIGHT TEXT”.

Does anyone have an idea as to what this is and the cause, and the proper way to fix it.

Might she have clicked on the ExcelDirect button or pressed Alt-X by mistake. That's an Excel communication error. Is Excel available on her machine?

yes Excel is available on her machine, so it is possibe.