I deleted internet data and other data to get more space on my internal memory. Now Twitter for HTC Sense will not work again and keeps telling me "multiple accounts are not supported". I do not have multiple accounts. But I can't get into this app to change anything. What should I do?
You could always clear the data for the app, if the app is simply kicking you out when you open it.
Go to Settings -> Applications -> Manage applications. Select your app, and click Clear Data. This will wipe all data from the app, as if you had uninstalled it and installed it fresh*.
*To be technical, it isn't the same as uninstalling and reinstalling because the dex files in the Dalvik Cache remain unchanged. Installing a fresh copy would regenerate those files. But it really shouldn't matter for non-developers.