Article credit: Sage 

Extreme slowness issues may be experienced on a workstation when using the AP or AR Enquiry feature. It may be that Evolution seems to freeze for up to 5 minutes.
It may even be that other users on the same network accessing the same company don’t experience the same slowness.

SOLUTION:

First ensure that all network connections between the server and the problematic workstation has been checked with no potential network reasons to be causing this problem.
A good idea here would be to execute a continues ping between the server and PC and vice versa to ensure no data packets are being lost (with the assistance of the client’s local IT consultant).

However, in a recent query the following solution resolved the matter:

a) Completely close Evolution on the specific PC where this problem occurs on;

b) Open the PC’s Registry by going to Start | Run (or the text field just on top of the Start button), insert the text: regedit and Enter on the keyboard; 

On the desktop of the PC, select the Windows key on the keyboard together with R on the keyboard to open the screen below, enter regedit below and enter on the keyboard to open the Registry Editor

c) In the Registry Editor, go to:

HKEY_CURRENT_USER\Software\Softline\Evolution\Agents\*XXX*

d) Right click on the \*XXX* folder and then delete it

XXX* above depends on the specific relevant agent name that encounters the problem on that specific PC. 

ADDITIONAL ADVICE

It may be that the Running Balance column has been added on the workstation’s AR / AP Enquiry grid.
It should therefore be advisable to simply remove this column, especially if the company has a significant number of customers/suppliers.