I have installed Ubuntu 12.04 64bit version alongside Windows 7 64bit from DVD following the instructions on THIS page. The entire installation went as described and there seemed to be no problems with it.
When I restarted I discovered there was no boot menu. I solved the problem as described on THIS link.
After rebooting again I got to the boot menu and chose the Ubuntu 12.04 option after which a black screen appeared with text:

Initializing variable space.

Starting cmain()..._

and after that nothing happens except that the dash blinks. It seems that I can't provoke any kind of response with enter space or any F keys. Here is a detailed report from EasyBCD if it's of any help:

There are a total of 2 entries listed in the bootloader.



Default: Windows 7

Timeout: 10 seconds

EasyBCD Boot Device: C:



Entry #1

Name: Windows 7

BCD ID: {current}

Drive: C:

Bootloader Path: Windowssystem32winload.exe



Entry #2

Name: Ubuntu 12.04

BCD ID: {b25a01ae-0cc9-11e3-bbfd-742f68d47a13}

Drive: C:

Bootloader Path: NSTAutoNeoGrub0.mbr



Windows Boot Manager

--------------------

identifier              {9dea862c-5cdd-4e70-acc1-f32b344d4795}

device                  partition=DeviceHarddiskVolume1

description             Windows Boot Manager

locale                  hr-HR

inherit                 {7ea2e1ac-2e61-4728-aaa3-896d9d0a9f0e}

default                 {e7a07940-8e20-11e1-a7a0-b36feede8885}

resumeobject            {e7a0793f-8e20-11e1-a7a0-b36feede8885}

displayorder            {e7a07940-8e20-11e1-a7a0-b36feede8885}

                        {b25a01ae-0cc9-11e3-bbfd-742f68d47a13}

toolsdisplayorder       {b2721d73-1db4-4c62-bf78-c548a880142d}

timeout                 10



Windows Boot Loader

-------------------

identifier              {e7a07940-8e20-11e1-a7a0-b36feede8885}

device                  partition=C:

path                    Windowssystem32winload.exe

description             Windows 7

locale                  hr-HR

inherit                 {6efb52bf-1766-41db-a6b3-0ee5eff72bd7}

recoverysequence        {e7a07941-8e20-11e1-a7a0-b36feede8885}

recoveryenabled         Yes

osdevice                partition=C:

systemroot              Windows

resumeobject            {e7a0793f-8e20-11e1-a7a0-b36feede8885}

nx                      OptIn



Real-mode Boot Sector

---------------------

identifier              {b25a01ae-0cc9-11e3-bbfd-742f68d47a13}

device                  partition=C:

path                    NSTAutoNeoGrub0.mbr

description             Ubuntu 12.04

Any kind of help is appreciated.