I tested this in the current release build, promis.e v8i Select Series 2 build 08.11.07.150. Using ANSI installs, I was not able to repeat any of these errors. So I switched to using IEC installs, and I was able to repeat the problem where the migrated symbols worked fine when placed, but were not editable int he AutoCAD version. When I tried to edit them I received an "unable to read write protected memory" error. Can any of you confirm or deny if that is the error message you are getting as well so I know if we are talking about the same problem?
Side note: Daniel, I was not able to repeat a problem where the symbols were not able to be inserted at all. Can you provide any more information about that error and its circumstances? It would probably be best if you submitted a service ticket for that, and probably a sample of your catalog to test.
After having the problem with the migration in the IEC 150 build, I switched to the previous build, promis.e V8i Select Series 1, build 08.11.07.82 and tried migrating from MicroStation to AutoCAD, and did not have any errors. The symbols placed fine and were editable with no errors in the AutoCAD version. Then I copied that AutoCAD version 82 catalog to my 150 build AutoCAD version and the symbols were editable in that version as well. So it looks like one possible workaround for now would be to migrate the catalog using the 82 build for AutoCAD.
I was never able to repeat the problem with the connection points being very large, but there was an existing defect in the system for that problem which is scheduled to be resolved in the next release, Select Series 3. So someone else was able to repeat it at some point. Also, this new defect with migrating using the 150 build and not editing the symbols is also resolved in Select Series 3. So very shortly there should be a permanent fix for this.