I've just had something very similar happen. Here's what I did.
1. Inserted the enhanced CD "Say You Will" by Fleetwood Mac.
2. Clicked on + next to "Say You Will" then + next to "Data" then clicked on the Xtras folder. The contents of the folder were displayed correctly. I never displayed the contents of the "Data" folder.
3. Clicked on the "Data" folder and got the message box "Gathering Information and updating view". MC9 stopped responding at this point.
The same thing happens if I click on the + next to "Say You Will" and then click on the "Data" folder.
Here are my details:
Media Center Registered 9.0.149 -- C:\Program Files\J River\Media Center\
Microsoft Windows XP Workstation 5.1 Service Pack 1 (Build 2600)
AMD Athlon 2020 MHz MMX / Memory: Total - 490 MB, Free - 78 MB
Internet Explorer: 6.0.2800.1106 / ComCtl32.dll: 5.82 (xpsp1.020828-1920) / Shlwapi.dll: 6.00.2800.1106 (xpsp1.020828-1920)
Shell32.dll: 6.00.2800.1145 (xpsp2.021108-1929) / wnaspi32.dll: Internal ASPI Layer
Ripping / Drive D: Copy mode:ModeBurstBigBuffer CD Type:Auto Read speed:Max
Digital playback: Yes / Use YADB: Yes / Get cover art: No / Calc replay gain: Yes / Copy volume: 32767
Eject after ripping: No / Play sound after ripping: No
Burning / Drive D: SAMSUNG CDRW/DVD SM-348B Addr: 1:0:0 Speed:4 MaxSpeed:48 Use MJ Engine:Yes
Test mode: No / Eject after writing: Yes / Direct decoding: Yes / Write CD-Text: No
Use playback settings: No / Normalization: None