My problems with the Raspberry Pi booting up have now been resolved.
When booting up using Raspbian OS - I was getting heaps of "timeout waiting for hardware interrupt" errors. The screen would scroll really quickly, then timeout errors would ensue, and it seemed like an endless loop. At first I could not get into recovery mode, but once I eliminated a 7-port powered USB hub from the equation, it would respond to the shift key (ie. by plugging keyboard and mouse directly into Rpi USB sockets). I tried installing some of the other operating systems that come with NOOBS, and I did not experience the hardware interrupt errors with the other operating systems, but when I installed Raspbian - the GUI would fail to boot. ANd I really wanted to to stick to Raspbian.
I did manage to get into the GUI every now and then by jumping into and out of the config file (in recovery mode), but this was not satisfactory.
I then experimented with booting without anything but an HDMI cable (and power) attached.
Suddenly, the GUI loaded without issue. I could then insert mouse and keyboard after the OS had booted up into the GUI.
I booted up with mouse inserted on its own. But when I tried keyboard on its own - the problem returned.
So this pointed to an issue with the keyboard. I was able to boot up without the keyboard and then successfully use the keyboard by plugging it in after boot up.
I then tried the RPi attached to a monitor instead of TV - by using a HDMI to DVI cable. I had no problem booting up with keyboard attached.
So I am putting my problem down to a combination of a
- rollup keyboard used in conjunction with a TV (using HDMI cable).
Possibly a power related issue - maybe the combination of keyboard and TV was drawing too much current from RPi on bootup? Who knows... but my problem is solved.
I now can boot up successfully without any further issue.