Hi,

I just found this in my dmesg:

[33331.244598] ***** DSPMMU FAULT ***** IRQStatus 0x2
[33331.244628] ***** DSPMMU FAULT ***** faultAddr 0x20c55000
[33331.244628] WMD_DEH_Notify: ********** DEVICE EXCEPTION **********
[33331.244659] WMD_DEH_Notify: DSP_MMUFAULT,errInfo = 0x0
[33331.244659] WMD_DEH_Notify: DSP_MMUFAULT, High Address = 0x20c5
[33331.244659] WMD_DEH_Notify: DSP_MMUFAULT, Low Address = 0x5000
[33331.244659] WMD_DEH_Notify: DSP_MMUFAULT, fault address = 0x20c55000
[33335.096771] ***** DSPMMU FAULT ***** IRQStatus 0x2
[33335.096801] ***** DSPMMU FAULT ***** faultAddr 0x210e0200
[33335.096832] WMD_DEH_Notify: ********** DEVICE EXCEPTION **********
[33335.096832] WMD_DEH_Notify: DSP_MMUFAULT,errInfo = 0x0
[33335.096832] WMD_DEH_Notify: DSP_MMUFAULT, High Address = 0x210e
[33335.096862] WMD_DEH_Notify: DSP_MMUFAULT, Low Address = 0x200
[33335.096862] WMD_DEH_Notify: DSP_MMUFAULT, fault address = 0x210e0200
[33358.936340] ***** DSPMMU FAULT ***** IRQStatus 0x2
[33358.936370] ***** DSPMMU FAULT ***** faultAddr 0x20b07000
[33358.936401] WMD_DEH_Notify: ********** DEVICE EXCEPTION **********
[33358.936401] WMD_DEH_Notify: DSP_MMUFAULT,errInfo = 0x0
[33358.936401] WMD_DEH_Notify: DSP_MMUFAULT, High Address = 0x20b0
[33358.936431] WMD_DEH_Notify: DSP_MMUFAULT, Low Address = 0x7000
[33358.936431] WMD_DEH_Notify: DSP_MMUFAULT, fault address = 0x20b07000
[33414.890380] ***** DSPMMU FAULT ***** IRQStatus 0x2
[33414.890380] ***** DSPMMU FAULT ***** faultAddr 0x22d45000
[33414.890411] WMD_DEH_Notify: ********** DEVICE EXCEPTION **********
[33414.890411] WMD_DEH_Notify: DSP_MMUFAULT,errInfo = 0x0
[33414.890441] WMD_DEH_Notify: DSP_MMUFAULT, High Address = 0x22d4
[33414.890441] WMD_DEH_Notify: DSP_MMUFAULT, Low Address = 0x5000
[33414.890441] WMD_DEH_Notify: DSP_MMUFAULT, fault address = 0x22d45000
[33424.024230] ***** DSPMMU FAULT ***** IRQStatus 0x2
[33424.024230] ***** DSPMMU FAULT ***** faultAddr 0x22f33000
[33424.024261] WMD_DEH_Notify: ********** DEVICE EXCEPTION **********
[33424.024261] WMD_DEH_Notify: DSP_MMUFAULT,errInfo = 0x0
[33424.024291] WMD_DEH_Notify: DSP_MMUFAULT, High Address = 0x22f3
[33424.024291] WMD_DEH_Notify: DSP_MMUFAULT, Low Address = 0x3000
[33424.024291] WMD_DEH_Notify: DSP_MMUFAULT, fault address = 0x22f33000

Does anyone know what that means? I'm using kernel-power 42 overclocked to 900 MHz.

Run your N900 at default clockspeed/voltage and see if the error occurs again.
Your DSP is overclocked by default as well when you're overclocking your CPU.