Check in Database view for Admin>Security to confirm the user has rights to see Proposals
Check in Database view that Constituent records have a tab for Prospect.  The Prospect Module (SEARCH Module) is an optional module and may not be included with your version of RE or RE NXT.

In NXT go to Config>Security>Security Group
Open a Security Group
Under Lists rights confirm that Access to opportunity lists is marked with Yes.  
If marked No, click Edit rights and change this selection to Yes.