Nimbostratus
You'll need to provide the error message and any additional information you have if you want help troubleshooting your iRule. I don't have an SAP environment available for test so there's no way I can reproduce your issue.
Based on the limited information in your post, I'd guess this is what you are running into: Internet Explorer file downloads over SSL do not work with the cache control headers
My suggestion would be to create two virtual servers, one for HTTP and another for HTTPS. Assign the built-in HTTP to HTTPS redirect iRule (_sys_https_redirect) and an HTTP profile to the HTTP virtual. For the HTTPS virtual, attach an SSL profile, HTTP profile, the SAP pool, and finally the original iRule that SAP gave you.
Give that a shot and it should work without needing to change any of the code. If you're still running into issues, post some further detail here and we'll do our best to give you a hand.
-George
