Just to add weight to this, I have exactly the same problem - post SP1 update to .0415. Followed the instructions to the letter. Get the screen flickering every couple of seconds as described above and weather fails to load.
I have shut down my Firewall and AV software completely and no avail - even though REXE + is enabled and no record of it being blocked in either. Other info as needed follows: 1.) Operating system and version (32bit or 64bit) - Win 7 Pro (Version 6.1.7601), SP1 64 bit 2.) RAM memory size - 16Gb 3.) Video card and memory size - Radeon HD 6950 2Gb 4.) Overclocking? - Yes @ 4.6GHz (as with previous version of REX Essential Plus) 5.) Total hard drive space - Total all PC - 3.8Tb (drive with REX install - 2Tb with 1.32Tb free) 6.) Using REX in a network or not - Not used in a network 7.) Which version of Flight Simulator installed (including service packs) - FSx - Version 10.0.61637.0, SP2 8.) Internet connection active or not - Yes. 9.) Which antivirus software running - NOD32 Antivirus 6 (v6.0.308.0), Full license 10.) Whether or not firewall running - ZA Pro (v 10.0.250.000) 11.) Whether or not you are utilizing FSUIPC - Yes, unregistered version 12.) If there are any error logs in the REX/ErrorLogs folder, make certain to include in your post. - None 13.) Is UAC turned OFF in Windows - Off 14.) What folder is REX installed in - F:\Games\FSx\REX Essential Plus (this drive does not contain my OS) 15.) What folder is FSX/P3D installed in - D:\FSx (dedicated SSD) 16.) Do you start REX by RIGHT CLICKING the exe file and selecting RUN AS ADMIN EACH time? No, set to run as administrator. Have also tried using right click 'Run as administrator'. 17.) What is your RATE AT WHICH WEATHER CHANGES OVER TIME set to in FS? - 'No change' 18.) Did you use a flightplan from REX when experiencing the error(s)? No 19.) Did you make changes to the CONFIGURATION screen or are ALL the settings stock? Yes see screenshots below 20.) What are your texture settings within the OPTIONS window? See screenshot below