Or if you can't, then taking a screenshot of the SDP payload protocol details in the INVITE and 200 response and posting them here? The graph shows fine for SIP+RTP captures I have, in wireshark 1.10.5. Maybe there's something odd in the SDP that prevents it from figuring out the RTP conversation. (do the packets display as RTP packets in the normal display window?)
This was tested on RouterOS v6.27 (mipsbe) and v6.28 (smips), but it should work mostly the same everywhere. I was using Windows 7 (64-bit) and Wireshark 1.12.6, on a Thinkpad X220 using the onboard gigabit ethernet port and Intel 6205 802.11n card.
Sometimes latest versions of the software can cause issues when installed on older devices or devices running an older version of the operating system. Software makers usually fix these issues but it can take them some time. What you can do in the meantime is to download and install an older version of WireShark 1.10.1 (64-bit).
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