I am not aware of any (but that does not mean no issues exist). What error do you receive when attempting to install MA 4.5?
The agent does install - the swinstall log shows the agent install without errors.
However when the agent is started it fails and generates a coredump.
I have about 20 or so HP UX 11.23 systems and only a few systems does this issue occur on.
The UNIX 4.0 agent installs and runs on all systems.
You may want to check the release notes for MA 4.5 and confirm that the agent is compatible with whatever kernel version you are using. I suspect it is because you indicated that MA 4.0 is working but its still worth a check. Other than that you will probably need to open a case with support. You could try posting the dump here (assuming its not to large) and we can try to analyze it to see what is going on but if it actually requires some sort of code fix to resolve you'll have to open a case.