MB Read Holding Register Error

I am receiving the following error when using the MB_03_Read_holding_Registers Subroutine.
-12 Invalid Table Index Line 4 ntReceive_Table
I am using this subroutine to read data from several Modbus devices and I have had no problems with it until I recently tried reading data from an Obvius AcquiSuite A8812. I have verified that all the table types and register lengths are compatible. What am I missing?

P.S. It was working without a problem for several hours before the problem showed up.

The table length is 260, which is the maximun legal length for a packet.
You may want to step into the subroutine and check how many characters you are recieving.