The above memory error message is very generic and doesn't always identify the real cause of the issue. Anyways it is considered this is due to corrupt toolbar file. So try the solution given here:
1. Close Excel (if it is open)
2. Reboot if needed.
3. And locate all files (with Start > Search etc) with extension .xlb
4. Rename the extension(s) like .old
5. Start XLS file again.
It is also recommended to verify and install the latest updates, this is very helpful in fixing many common excel problems.