When clicking on the "Activity List View" button from the Homepage, the List View that's loaded by default is the last View that was used/viewed by the User in question. In some cases, the criteria to be loaded for the View is too broad, and as a result this page will never load, resulting in a "time limit exceeded" error.
Here's how to fix it
1. Create a new Activity List View with this URL: https://na4.salesforce.com/ui/list/FilterEditPage?ftype=z&retURL=%2F007
Note: The URL will have to be changed depending on the instance the your Organization is on. E.g.
2. Set the scope to "My Activities," and "Due Date equals today," and then click Save.
3. When the view finishes loading, view the page source code in any text editor, and look in the code for the List View drop-down names. You'll see some List View IDs there too, like this:
<option value="00B30000001DFZW">All Activities</option>
<option value="00B30000002ZfOU">List View That Times Out</option>
<option value="00B30000002ZBff">Open Activities</option>
<option value="00B30000002D0sF" selected>test for deletion</option>
<option value="00B30000001DFZX">Today's Activities</option>
<option value="00B30000001DFZY">Upcoming Events</option>
The easiest way to find the List View list in the source code is to do a Ctrl+F search for "option value" until you find the list view names that are in the activity view Picklist.
4. Using the ID for the List View that is timing out, paste it into the following edit view URL (substituting for the ID with the one that needs to be deleted/edited):
Again, the instance used in the URL will differ depending on the instance the customer is on.
5. Click Delete, or make the view criteria more specific to avoid the timeout.