Page selection popup error



We have created custome property types using base as Page type property in Episerver5, now we have migrated application to Episerver CMS 7
 When we try to access page structure in Edit mode it gives following error message, Can you please help us?
 Siden kunne ikke lastes inn

Koblingen som du angav, virker ikke. Dette kan skyldes manglende vedlikehold eller at det er en feil med koblingen.
Detailed error information (authorized by permissions to functions)
Error occured 22.09.2014 08:36:36

User Agent Mozilla/5.0 (Windows NT 6.1; WOW64; rv:32.0) Gecko/20100101 Firefox/32.0
Url https://testserver:443/EPiServer/CMS/edit/pagebrowser.aspx?id=6426&disablecurrentpageoption=False&info=FullRegion_ArticleLink3_ctl00_Display&value=FullRegion_ArticleLink3_ctl00_Value&epslanguage=no&displaywarning=False&requireurlforselectedpage=false
Referer https://testserver/EPiServer/CMS/Home

PageReference: Input string was not in a correct format.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: EPiServer.Core.EPiServerException: PageReference: Input string was not in a correct format.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of

Sep 22, 2014 10:01
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