OE Order Posting extremely slow

Hi,

Recently we upgraded to Sage 300 ERP 2014 (with latest service packs) and OE Order Posting became extremely slow. Most of the time it is taking 20 minutes to post an order. Though it happens intermittently but we got extremely frustrated with this situation. Following is the environment:

ACCPAC Server: Windows 2008 R2 Server (64Bit HP Server Intel Xeon CPU E5-2650 2.00 GHz 2 Processors, 32GB Ram)

On partition D:\ (4.54 TB total and free space is 3.86 TB)

Microsoft SQL 2008 R2 database on the same server

15 ACCPAC Users

Inventory Setup - "Cost Items During Posting" (we have been using this option since previous versions)

We checked hardware, switches, and network and couldn't find any problem. Problem is only in OE Order Entry posting in all the workstations for all the users.

Please advise on what we are missing or we should do to fix this problem.

Many thanks!