Boot time iwlwifi and acpi object errors

I am getting boot time errors in ubuntu 14.04. After booting it works without any problem. Errors displayed are:

0.669116] dmar: Failed to find handle for ACPI object SB.PCI0SD

After SD some numbers are also displayed( I could not capture them). This error is displayed in black screen.[Next this error is shown(http://http://i.stack.imgur.com/Ybg0M.jpg)]
Also its written 'ubuntu 14.04' rather than 'ubuntu' while starting as can be seen in image. These all happened suddenly.
Output of dmesg |grep iwl is:

[ 16.302012] iwlwifi 0000:03:00.0: loaded firmware version 25.17.12.0 op_mode iwlmvm
[ 18.182318] iwlwifi 0000:03:00.0: Unsupported splx structure
[ 18.268492] iwlwifi 0000:03:00.0: Detected Intel(R) Dual Band Wireless AC 3160, REV=0x164
[ 18.268837] iwlwifi 0000:03:00.0: L1 Enabled - LTR Enabled
[ 18.269360] iwlwifi 0000:03:00.0: L1 Enabled - LTR Enabled
[ 18.490087] ieee80211 phy0: Selected rate control algorithm 'iwl-mvm-rs'
[ 22.183698] iwlwifi 0000:03:00.0: L1 Enabled - LTR Enabled
[ 22.185198] iwlwifi 0000:03:00.0: L1 Enabled - LTR Enabled

Changes done today can be seen in this imagehttps://drive.google.com/file/d/0B7v...ew?usp=sharing
I am new to ubuntu. Please help. Thanks in advance.