I have an HTC Incredible which continues to display low on disk space. I have posted in the past about this problem. I am blocked from accessing my Google talk and Gmail. This has become a routine problem. I have tried to restart and update my system however everything is updated and this didn't help. My operating system is Android 2.3.4 I also tried to un-mount and remount the SD card where I have 1.6GB of free space. HTC told me "the low storage error is a general system error with the android operating system. There is no "fix" for the error per se, but careful management of your apps on the device can greatly reduce or correct its occurrence. If any apps become too full of data, this may cause a Low Storage error. This is not due to the phone running out of available storage, but that the app has reached the maximum allotted amount of space that it has been assigned. The error is most often caused by mail, text messages, or Facebook. Optimization of these apps is the key to solving this error."
HTC instructed me to manage apps and clear the data from Mail, Facebook, & Dialer Storage.
Here are their instructions
To see the data stored in an app, go to Menu > Settings > Applications > Manage applications > All > Menu > Sort by size.
In Mail tap on Menu > More > Settings > Send & receive. Look for things like attachment options, how far into the past you get mail, size limits, and downloading headers only.
If you have multiple email accounts, the settings will need to be adjusted for each one. Obviously the more accounts you have, the higher the chance that this error may present itself.
If your Mail is still having the issue after clearing out old messages and optimizing the settings, you may need to remove and re-add the account. Once removed, connect the phone to your PC in Disc Drive mode, open the removable drive (under My Computer), and delete the mail folder located in Removable Drive/.data/mail. This is the storage folder for mail temp files. Deleting this folder in addition to removing the account should alleviate the error message for you. Just re-add the account after you delete the mail folder.
Text messages and Facebook may cause this error as well, so make sure you manage the size of these accounts too. If you use text messaging a lot and like to keep old messages, you may want to consider using a backup app like Handy Backup or SMS Backup & Restore. These are free apps from the market that can create a data file to store messages for you which can be retrieved later.
If the issue is being caused by Facebook, then signing out of Facebook for HTC Sense should help. Go to Menu > Settings > Accounts & sync > Facebook for HTC Sense > Remove account. Then soft reset the phone by powering off, remove the battery for at least 30 seconds, replace, reboot, and add Facebook for HTC Sense back to accounts & sync. You may also want to clear data from Facebook for HTC Sense and the Facebook widget if you use it. Do this in the manage applications area.
As always, HTC is there to answer any technical questions or concerns you may have between 6am to 1am EDST, 7 days a week for your convenience, by phone at 1-866-449-8358.