NW2007-NW2010: Failed to publish workflow

I have a big working workflow that I am importing into NW2010 from NW2007.  The workflow saves fine but when I try to publish it in NW2010 it shows me these errors:

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Server was unable to process request. ---> Failed to publish workflow: 

<Error><CompilerError Line="0" Column="0" Text="Activity 'addToHashtableActivity8' validation failed: Path resolved to Referenced activity Property 'ReturnValue' whose PropertyType 'System.Int32' does not match with the Target Type 'System.String'." />

<CompilerError Line="0" Column="0" Text="Activity 'addToHashtableActivity9' validation failed: Path resolved to Referenced activity Property 'ReturnValue' whose PropertyType 'System.Int32' does not match with the Target Type 'System.String'." />

<CompilerError Line="0" Column="0" Text="Activity 'addToHashtableActivity12' validation failed: Path resolved to Referenced activity Property 'ReturnValue' whose PropertyType 'System.Int32' does not match with the Target Type 'System.String'." />

<CompilerError Line="0" Column="0" Text="Activity 'addToHashtableActivity15' validation failed: Path resolved to Referenced activity Property 'ReturnValue' whose PropertyType 'System.Int32' does not match with the Target Type 'System.String'." />

<CompilerError Line="0" Column="0" Text="Activity 'addToHashtableActivity20' validation failed: Path resolved to Referenced activity Property 'ReturnValue' whose PropertyType 'System.Int32' does not match with the Target Type 'System.String'." />

<CompilerError Line="0" Column="0" Text="Activity 'addToHashtableActivity21' validation failed: Path resolved to Referenced activity Property 'ReturnValue' whose PropertyType 'System.Int32' does not match with the Target Type 'System.String'." />

<CompilerError Line="0" Column="0" Text="Activity 'addToHashtableActivity24' validation failed: Path resolved to Referenced activity Property 'ReturnValue' whose PropertyType 'System.Int32' does not match with the Target Type 'System.String'." />

<CompilerError Line="0" Column="0" Text="Activity 'addToHashtableActivity25' validation failed: Path resolved to Referenced activity Property 'ReturnValue' whose PropertyType 'System.Int32' does not m… 

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 How do I know which activity the error referring to? Anyone?