You cannot open Microsoft Dynamics GP now because another user is entering Multicurrency access information.

Other than having to define a functional currency to use econnect, I've never had the need to work with multiple currencies in GP until yesterday.  A colleague and I had defined the Singapore dollar and were in the process of granting the company access to the currency and to the exchange tables, when GP appeared to hang, giving the infamous "Not Responding" status.  We closed GP and attempted to get back in, however we were greeted with the message below:

 

I'd never bumped into this message before and my Google searches didn't seem to be bringing up anything very promising.  We removed our login from the ACTIVITY table, but still got the message.  We checked the usual suspects - SY00500, SY00800, SY00801, but still no luck.  We had 25 other users in the system and getting them all out wasn't an option, so we hadn't cleared the ACTIVITY, SY00800, SY00801 tables.  After sweating a bit, as users were unable to login to any company in GP, I found the line I was looking for in the ACTIVITY table:

We deleted the record where the USERID field was MC Access Setup, and users were able to login to GP again.