Switching from MPEG2 to H264 freezes MediaPortal

[deniax]

MediaPortal Version: svn--03-31-2007--01-01-Rev13718
MediaPortal Skin: BlueTwo wide
Windows Version: XP-MCE SP2
CPU Type: AMD 64 4000+
HDD: 4x Maxtor 250GB in Raid 0+1
Memory: 1GB
Motherboard: Asus A8N32-SLI
Motherboard Chipset: Nforce 4
Motherboard Bios: AMI (bios version 1303)
Video Card: Nvidia 7800GT
Video Card Driver: 93.71
Sound Card: Creative X-FI
Sound Card AC3: Creative X-FI
Sound Card Driver: 2.09.0007
1. TV Card: FireDTV
1. TV Card Type: DVB-C
1. TV Card Driver: BDA 4.7 (15.2.2007)
2. TV Card:
2. TV Card Type:
2. TV Card Driver:
3. TV Card:
3. TV Card Type:
3. TV Card Driver:
4. TV Card:
4. TV Card Type:
4. TV Card Driver:
MPEG2 Video Codec: Cyberlink Video/SP BD-HD Decoder (PDVD7.x)
MPEG2 Audio Codec: Cyber;ink Audio Decoder (PDVD)
Satelite/CableTV Provider: Casema
HTPC Case: Zalman HD160
Cooling: 4 Papst fans, Zalman VF700, Zalman CNPS7500
Power Supply: Enermax 500watt
Remote: MCE
TV: Sony 46x2000
TV - HTPC Connection: DVI

Additional info: using TV-Server 3

When I'm switching through normal SD channels which are encoded with MPEG, there is no problem. When I switch to the HD channels, which some of them are H264, the following happens (in no particular order)

1) The timeshift of another TV program is shown (!)
2) Nothing is shown, I have to disable and enable the TV to have an image

I've tried different codecs, and I'm not entirely sure that the problem is with the mpeg2/h264 switch...

To simplify the problem, I've recorded it You can have a peek here:
http://bob.gamepoint.net/mediaportal.mp4

The steps you see:
1) Normal SD (boring talkshow)
2) Switching to HD (Film HD)
3) Screen turns black
4) Switch TV off and on again
5) Film HD works
6) Selecting another HD source (National Geographic), works directly
7) Selecting yet another HD source (Discovery HD) [b]the previous channel is shown with the same (timeshifted?) material)
8) Switch TV off and on again fixes the problem and shows Discovery HD again
9) above steps are repeated