If any developers out there have tried embedding ActiveX controls into forms you will know all about this error. It basically locks Notes in an Error loop and you have to kill Notes to try again.
The error is caused by an incompatibility between Notes and ActiveX Control error events. Any ActiveX control that has an error event will cause the Generic LSE Error on Compile (Save) of the form.
The workaround (until Lotus fixes it properly), is simple and it works. When you open the database in design, simply run the form with the embedded control (by Design Test, or Preview in Notes). This seems to register with Notes that there is a control and the error event is bypassed. You can then happily go about editing and coding in the form with no Generic LSE Error. Note: There is no effect to the end user.
The only problem is that you must do this each time you start Notes. A small price to pay (a few seconds) to remove this very annoying error.