How is your setup. 1 disk, 2 partitions? Or 2 disks, both 1 partition?
It looks to me bootmgr is looking to wrong partition or cannot access the OSx partition.
Install osx on a secondary HDD, so the boot mgr would still be on the primary HDD (Windows 7 partition), switch startup disk, so osx would write its boot mgr on its own disk and this way, the boot mgr wouldn't be overwriten by Windows 7.
This way, you can boot osx in 2 ways, through the startup disk setting in BIOS itself (not so very pratical but a nice back door if needed), or by changing back the startup disk to the Windows 7 partition and booting through easybcd bootmgr.