Not being familiar with your phone some of these suggestions may not be available.
403 usually means APN (Access Point Name) error or a few other things.
Usually you need to clear all data out from Google Play Store, Google Service Framework and Download Manager. Without having to perform factory reset, you could try removing your google account in system settings -- Accounts -- Google -- remove your account. Get it off the phone. Then in settings, Apps, All, Force Stop Clear Data for the above three, Google Play, Google Service Framework and Download Manager. Feel free to force stop and clear data from any other heavily used apps and then reboot the device. When it starts back up, go back to Settings Accounts, Add Account -- add your google account back in. (All that data will come back down eventually, save for a few pieces) Now go back ointo Market and youll have fresh start.
OR
Clear your proxies out. Settings - Wireless Networks - More - Mobile Networks
youll see APN -- MOWAP - Edit that to clear out Proxy. You want to clear it out, proxy to be empty.
Now go back to Google PLay and try again.
OR
get on Wifi and try.