My EC2 instance suddently stops working. Restarting and stop/start server not help.

Dear All My EC2 Instance suddently stop working and now I cannot do anything for it. Restarting and stop/start does not help. Now the server is inaccessible. Could you please help to check as soon as possible? It's live service. I just see thee error log in Get system log.

Xen Minimal OS!

  start_info: 0xccd000(VA)

    nr_pages: 0x64366

  shared_inf: 0x6b728000(MA)

     pt_base: 0xcd0000(VA)

nr_pt_frames: 0xb

    mfn_list: 0x9ab000(VA)

   mod_start: 0x0(VA)

     mod_len: 0

       flags: 0x300

    cmd_line: root=/dev/sda1 ro console=hvc0 4

  stack:      0x96a100-0x98a100

MM: Init

      _text: 0x0(VA)

     _etext: 0x7b824(VA)

   _erodata: 0x97000(VA)

     _edata: 0x9cce0(VA)

stack start: 0x96a100(VA)

       _end: 0x9aa700(VA)

  start_pfn: cde

    max_pfn: 64366

Mapping memory range 0x1000000 - 0x64366000

setting 0x0-0x97000 readonly

skipped 0x1000

MM: Initialise page allocator for ff9000(ff9000)-64366000(64366000)

MM: done

Demand map pfns at 64367000-2064367000.

Heap resides at 2064368000-4064368000.

Initialising timer interface

Initialising console ... done.

gnttab_table mapped at 0x64367000.

Initialising scheduler

Thread "Idle": pointer: 0x2064368050, stack: 0x11d0000

Thread "xenstore": pointer: 0x2064368800, stack: 0x11e0000

xenbus initialised on irq 3 mfn 0xfeffc

Thread "shutdown": pointer: 0x2064368fb0, stack: 0x11f0000

Dummy main: start_info=0x98a200

Thread "main": pointer: 0x2064369760, stack: 0x64000000

"main" "root=/dev/sda1" "ro" "console=hvc0" "4"