MKVs (1080p) require buffering all the time after 1.2 firmware upgrade

After upgrading my Boxee Box to the 1.2.0 firmware I got A LOT of buffering when playing 1080p MKV movies.
I don't think it has anything to do with the particular media files because when starting any local movie, the pre-buffering is much longer with 1.2.0 than the previous 1.1.2.

I have reverted back to 1.1.2 and the problem went away. Now I have upgraded again to 1.2.0.20310 (to make this jira ticket) and the problem is here again.

The setup is NAS Synology 411j. Wired connection through a 1gbit switch. Using SMB.

Here's the info from one of the files that get a lot of buffering:

Complete name : I:\Cartoon\The Incredibles (2004)\The Incredibles (2004).mkv
Format : Matroska
Format version : Version 2
File size : 9.29 GiB
Duration : 1h 55mn
Overall bit rate : 11.5 Mbps
Movie name : The Incredibles 2004
Encoded date : UTC 2011-06-19 09:45:24
Writing application : mkvmerge v4.4.0 ('Die Wiederkehr') built on Oct 31 2010 21:52:48
Writing library : libebml v1.0.0 + libmatroska v1.0.0

Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L4.0
Format settings, CABAC : Yes
Format settings, ReFrames : 3 frames
Codec ID : V_MPEG4/ISO/AVC
Duration : 1h 55mn
Bit rate mode : Variable
Bit rate : 6 819 Kbps
Maximum bit rate : 25.0 Mbps
Width : 1 920 pixels
Height : 1 080 pixels
Display aspect ratio : 16:9
Frame rate : 23.976 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.137
Stream size : 5.30 GiB (57%)
Writing library : x264 core 114 r1924 08d04a4
Encoding settings : cabac=1 / ref=3 / deblock=1:0:0 / analyse=0x3:0x133 / me=umh / subme=7 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=1 / chroma_qp_offset=-2 / threads=6 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / constrained_intra=0 / bframes=3 / b_pyramid=0 / b_adapt=1 / b_bias=0 / direct=1 / weightb=1 / open_gop=0 / weightp=2 / keyint=240 / keyint_min=24 / scenecut=40 / intra_refresh=0 / rc_lookahead=40 / rc=2pass / mbtree=1 / bitrate=6819 / ratetol=1.0 / qcomp=0.60 / qpmin=0 / qpmax=69 / qpstep=4 / cplxblur=20.0 / qblur=0.5 / vbv_maxrate=25000 / vbv_bufsize=25000 / nal_hrd=vbr / ip_ratio=1.40 / aq=1:1.00

Audio #1
ID : 2
Format : DTS
Format/Info : Digital Theater Systems
Format profile : ES
Codec ID : A_DTS
Duration : 1h 55mn
Bit rate mode : Constant
Bit rate : 1 510 Kbps
Channel(s) : 6 channels
Channel positions : Front: L C R, Side: L R, LFE
Sampling rate : 48.0 KHz
Bit depth : 24 bits
Compression mode : Lossy
Delay relative to video : 11ms
Stream size : 1.22 GiB (13%)
Language : English

Audio #2
ID : 3
Format : AC-3
Format/Info : Audio Coding 3
Mode extension : CM (complete main)
Codec ID : A_AC3
Duration : 1h 55mn
Bit rate mode : Constant
Bit rate : 640 Kbps
Channel(s) : 6 channels
Channel positions : Front: L C R, Side: L R, LFE
Sampling rate : 48.0 KHz
Bit depth : 16 bits
Compression mode : Lossy
Stream size : 528 MiB (6%)
Language : Danish

Audio #3
ID : 4
Format : AC-3
Format/Info : Audio Coding 3
Mode extension : CM (complete main)
Codec ID : A_AC3
Duration : 1h 55mn
Bit rate mode : Constant
Bit rate : 640 Kbps
Channel(s) : 6 channels
Channel positions : Front: L C R, Side: L R, LFE
Sampling rate : 48.0 KHz
Bit depth : 16 bits
Compression mode : Lossy
Stream size : 528 MiB (6%)
Language : Norwegian

Audio #4
ID : 5
Format : AC-3
Format/Info : Audio Coding 3
Mode extension : CM (complete main)
Codec ID : A_AC3
Duration : 1h 55mn
Bit rate mode : Constant
Bit rate : 640 Kbps
Channel(s) : 6 channels
Channel positions : Front: L C R, Side: L R, LFE
Sampling rate : 48.0 KHz
Bit depth : 16 bits
Compression mode : Lossy
Stream size : 528 MiB (6%)
Language : Swedish

Audio #5
ID : 6
Format : AC-3
Format/Info : Audio Coding 3
Mode extension : CM (complete main)
Codec ID : A_AC3
Duration : 1h 55mn
Bit rate mode : Constant
Bit rate : 640 Kbps
Channel(s) : 6 channels
Channel positions : Front: L C R, Side: L R, LFE
Sampling rate : 48.0 KHz
Bit depth : 16 bits
Compression mode : Lossy
Stream size : 528 MiB (6%)
Language : Finnish

Audio #6
ID : 7
Format : AC-3
Format/Info : Audio Coding 3
Mode extension : CM (complete main)
Codec ID : A_AC3
Duration : 1h 55mn
Bit rate mode : Constant
Bit rate : 640 Kbps
Channel(s) : 6 channels
Channel positions : Front: L C R, Side: L R, LFE
Sampling rate : 48.0 KHz
Bit depth : 16 bits
Compression mode : Lossy
Stream size : 528 MiB (6%)
Language : Icelandic

Text #1
ID : 8
Format : UTF-8
Codec ID : S_TEXT/UTF8
Codec ID/Info : UTF-8 Plain Text
Language : Danish

Text #2
ID : 9
Format : UTF-8
Codec ID : S_TEXT/UTF8
Codec ID/Info : UTF-8 Plain Text
Language : English

Text #3
ID : 10
Format : UTF-8
Codec ID : S_TEXT/UTF8
Codec ID/Info : UTF-8 Plain Text
Language : English

Text #4
ID : 11
Format : UTF-8
Codec ID : S_TEXT/UTF8
Codec ID/Info : UTF-8 Plain Text
Language : Norwegian

Text #5
ID : 12
Format : UTF-8
Codec ID : S_TEXT/UTF8
Codec ID/Info : UTF-8 Plain Text
Language : Swedish

Text #6
ID : 13
Format : UTF-8
Codec ID : S_TEXT/UTF8
Codec ID/Info : UTF-8 Plain Text
Language : Finnish

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