ah , the ever faithfully failing razer firmware and driver issue...
Lets see if this help you :
http://help.razersupport.com/us-en/faqlist.asp?sid=054224100701196038152004&pid=1621&pnm=Razer+Lachesis&seid=400002027&pos=Windows+7&top=Firmware+Updateroducts Platforms Topics FAQs
RAZER LACHESIS : WINDOWS 7 : RESOLUTION 400002628
Q: How can I update the firmware on my Lachesis if I have Windows 7?
A: The firmware update for the Razer Lachesis needs to be performed on a system running Windows XP or Vista. Be sure to have the most current drivers installed on that system prior to performing the update. Once the firmware on the Lachesis is successfully updated, the mouse should work on your Windows 7 system.
Driver link :
http://www.razersupport.com/index.php?_m=downloads&_a=viewdownload&downloaditemid=353&nav=0,76,18Firmware Link :
http://www.razersupport.com/index.php?_m=downloads&_a=viewdownload&downloaditemid=422&nav=0,76,18Firmware Update Guide Link :
http://www.razersupport.com/index.php?_m=downloads&_a=viewdownload&downloaditemid=139&nav=0,76,18So basicaly my Razer mouse had the same problem - its a firmware issue on the mouse...
I would suggest you use a XP pc and install the driver and then follow the update guide for the firmware... if the firmware updated correctly, it should say v1.94 in the Razer App , if it does not, then do the upgrade until it does - this could take some time, took me about 3/4 tries...
Once the firmware has been updated and shows that the mouse has the latest version of the firmware, go to your Windows 7 pc.. uninstall the driver for windows 7 that you have at the moment, make sure you clean any razer software from your registry that is linked to the mouse software - you can use the ccleaner app available for free from uncle google or manual regedit for this... razer does not like software versions being overinstalled or updated..
once the software is completly removed, and the pc was restarted, install the latest version software (link above) , but dont plug in your mouse!!!! after installation , restart your pc , and only then plug in the mouse. it will install the mouse, and then check your software , it will show you that your mouse is plugged in and the new firmware is installed..
Hope this helps!