silverlight - Exception - "Value does not fall within the expected range.inPage.xaml" -

i create app on windows phone 8 use mvvmcross , async sqlite.net. when go page exception:

system.argumentexception: value not fall within expected range.inpage.xaml'. @ system.windows.navigation.pageresourcecontentloader.endload(iasyncresult asyncresult) @ system.windows.navigation.navigationservice.contentloader_beginload_callback(iasyncresult result) @ system.windows.navigation.pageresourcecontentloader.beginload_onuithread(asynccallback usercallback, pageresourcecontentloaderasyncresult result) @ system.windows.navigation.pageresourcecontentloader.<>c__displayclass4.<beginload>b__0(object args) 

how determine source of problem?

had errors too. visualstate value not converted. copied example my answer here

<discreteobjectkeyframe keytime="0:0:0" value="true"/> 

versus

<discreteobjectkeyframe keytime="0:0:0">     <discreteobjectkeyframe.value>         <system:boolean>true</system:boolean>     </discreteobjectkeyframe.value> </discreteobjectkeyframe> 

so when not happen every time may example happening when coincidentally hover mouse on area , problem sits somewhere in mouseover state definition.