The SL500 doesn't have a Lenovo Windows 7 image (see here), so I have used my own licence of Windows 7, which is supported on this machine (see here).
So, after I used ThinkVantage System Update (TVSU), which I use and recommend as best practice for many years now, we found we could no longer connect to our Virgin Mobile Broadband (an Australian WWAN provider)with my internal Wireless WAN (WWAN) card, Ericson E3507g . When I used the USB WWAN Modem that came from my ISP, it worked fine, so I knew the issue wasn't with my provider.
The hard work
I tried rolling back drivers and software, no change. I kept getting either errors about not being able to authenticate the WWAN connection or that the provider couldn't be found.
After pulling my hair out, I made an complete backup to my server using Rescue & Recovery, and installed a vanilla copy of Windows 7 Professional 64bit, wiping the HDD clean & disabling Windows Update in the process.
I then installed only the requirements for the latest version of ThinkVantage Access Connections (TVAC), see here, but still I had the same issue.
Again, went back to a clean vanilla copy of Windows 7, and installed everything as before, except the older WWAN drivers from here, but still no success. Now it appears the newer version of TVAC can't work with the older version of the WWAN drivers.
Once again, went back to a clean vanilla copy of Windows 7, and installed everything as before, except using the newer WWAN drivers with the older verison of TVAC (v5.50) from here, still no success.
One last time, clean vanilla install, used the older WWAN driver with the older TVAC, and now my WWAN connects everytime without issues.
ThinkVantage Access Connections version 5.50
Ericsson Wireless drivers linked above (Programs & Features under Control Panel show this to be version 1.0.1046.226)
Also, if it helps, I have gone back to ThinkVantage System Update to install the rest of the Lenovo software, but clicked on "Do not show this update" against the following... (you see this when clicking on the [+] next to the item)
ThinkVantage Access Connection (TVAC) version 5.61
HSPA Wireless WAN Adapter driver for Windows 7 version 188.8.131.52
ThinkVantage GPS version 2.60, this is because it will install the HSPA WWAN driver above that I don't want
By hiding these 3 items, everything else has installed fine, and my WWAN is still working perfectly