I have found a solution to solve the hardware problem with the LG E900 Optimus 7,
showing the message 'Memory card not working' Your memory card has changed, is damaged or is non-compatible.
Flashing a new firmware or restoring images with zune does not solve the problem!
This message, if shown on a LG E900, implicates a hardware error with the NAND flash memory,
a Toshiba THGBM2G7D4FBAI9.
The memory chip is soldered to the top layer of the 2-layer mainboard, together with the led, sim card holding, head phone jack...
You can see it in the middle of this pic:
The hadware error is probably issued by broken solder joints, in turn probably issued by changes in temperature and/or physical exposure.
Following solution worked for me: (tried with one phone one month ago)
I heated the Toshiba memory chip with a heat tool with around 200 degrees Celsius (400 degrees Fahrenheit) for around ten minutes,
this is a technique sometimes used to repair broken graphic cards, please search google for this if you think there's something fishy going on here.
I used a 340 degree heat tool, with a 2cm distance first until I saw some solder balls, 'dripping' out, I increased the distance to 5cm.
After reasembling the phone works and does still work without problems.
Although this worked for me, it does not mean that it will work for you too.
Please try and comment, if it worked for you!!
Heating the memory chip should solve the problem not only temporary, if you get the same message some time afterwards, try again with more degrees (max 300) and/or a longer period (max 30min)
If you do not have the ability to heat the memory chip with a heat tool, you may trie to bake the whole mainboard layer. A problem could be a smelting head phone jack.
More information, pics at the www: manuga.bplaced.de
(i'm a new user and not allowed to post outside links)
If you find some language, logic or explanation mistakes in here, please tell me!
I hope that I find time to provide more information on the website mentioned above, I currently do not have much time to provide detailed phone dissasemble, assemble information, please search youtube for such vids.
Feel free to ask any questions in this thread or on my website.