Extjs v3 has lacked IE10 support too long already. IE10 has been in preview on win 7 for over 3 months so this should not be a surprise. 90% of Windows 7 machines will be auto updated to IE10 breaking our extjs apps. It can't be that much effort for Sencha to fix this issue. To continue to ignore v3 will be disastrous for your customers. Please do what is right and fix this asap. Thanks.