I'm new to Sage 100, so please be gentle!  lol 

We're running version 4.50.7.0. Today all users who tried to create a new Sales Order in Company HS1 received this message, "The sales order is already used.  Do you want to continue?" They start in Sales Order Entry and click on the "Next" icon that is next to the magnifying glass icon. The Sales Order Entry box appears with an order number and then the error message immediately appears. 

When I tested this, I get the same results. I noticed that the system showed a Sales Order number, so I researched it. There is no existing Sales Order with that number. The number is also not in sequence and is between two Sales Order numbers that were used in March of last year for company SC4. Doesn't Sage assign numbers in sequence?  If I'm in one company should Sales Orders from another company display in the search results? 

There were no changes that I am aware of or that anyone has confessed to. Any thoughts on how to fix this?