I had same problema and I could connect online:
My pc: windows 7 64bits
RSLogix 500 Pro 8.10.00 (CPR 9)
RSLinx Classic 2.59.00 CPR 9 SR 5
RSLogix Emulate 500 6.00.00.07 (CPR9)
I did these steps:
Open the Registry Editor (Start-->Enter regedit in the open field).
Go to HKEY_LOCAL_MACHINE-->SOFTWARE-->Wow6432Node-->Rockwell Software-->RSLinx-->Loadable Drivers.
Right Click on Loadable Drivers and select New-->Key and name the key EMU500
Right click on EMU500 and select New-->DWORD (32-bit) Value. The name of the key should be AutoLoad. Double click on the AutoLoad to open the Edit DWORD (32-bit) Value dialog. Enter 0 under Value Data and select Hexadecimal under Base. Click OK button when finished.
Right click on EMU500 again from the left-hand side and select New-->DWORD (32-bit) Value. The name of the key should be DriverID. Double click on the DriverID to open the Edit DWORD (32-bit) Value dialog. Enter 13 under Value Data and select Hexadecimal under Base. Click OK button when finished.
Right click on EMU500 and select New-->DWORD (32-bit) Value. The name of the key should be Flags. Double click on the Flags to open the Edit DWORD (32-bit) Value dialog. Enter 2 under Value Data and select Hexadecimal under Base. Click OK button when finished.
Right click on EMU500 and select New-->String Value. The name of the key should be Description. Double click on the Description to open the Edit String dialog. Enter SLC 500 (DH485) Emulator driver under Value Data. Click OK button when finished.
Right click on EMU500 and select New-->String Value. The name of the key should be DLL. Double click on the DLL to open the Edit String dialog. Enter ABEMU5.DRV under Value Data. Click OK button when finished.
The SLC (DH485) Emulator Driver should now appear available in RSLinx to configure.
Then, I opened Emulator and found my program and chose Station #00,
opened rslinx and chose Emulator driver, Station #01,
then opened rslogix 500 pro and found my program, I selected Comms/System Comms... Selected the processor that I named 00 and go Online from the same window... it still appearing the same text "not able to star emulator"but when I pushed "Ok"... Now is Online!!!
Hope this info help you... I apologize for my English...