n addition to what IBM has suggested, try the below as well. Have had a lot of users experiencing this issue and the following managed to stop the Notes IPC Asynch Message processor (1) error from re occurring.
(1) IN addition to deleting the cache, bookmark and desktop delete the workspace folder
(2) Open regedit and navigate to HKEY_CLASSES_ROOT.
Delete all the keys and all entries under the keys: HKEY_CLASSES_ROOT\Notes, HKEY_CLASSES_ROOT\Notes.Link,
(3) Run the Lotus Notes installation cd and select the option “Repair”.