Sometimes it can take longer than expected to change users in Quicklaunch, below are some tips on how to improve the action.
Multiple Exchange Domains
If the accounts being switched are on different Exchange domains, you may need to add additional Domains in the settings.
1. From within Quicklaunch select settings <CTRL-ALT-S> and click on the Account tab on the left
2. Click "Show Advanced Settings" under Options if they are not already shown, then click on the Domains tab
By default, there should be a domain listed for the default account that is used to log into Quicklaunch.
3. Click the '+' button below the list of domains
4. Configure the new domain
5. Click Save