Sorry, but I have only bad news...
I try to resolve whats is this VT_PTR data type (in C++ VT_PTR is constant, but VT_PTR looks like VarianT PoinTeR). I check link, which gives you Michael Ascherman in the same thread (Thanks to Michael :-); Q177575 - PRB: ActiveX Controls Passing Variant Back to VFP Cause Error). There are one example how you can simulate this error: I build sample control in VC++ and import it in VB; ObjectBrowser says "MyMethod(SampleParam)" (in VB this is equivalent to "MyMethod(SampleParam As Variant)"); THERE ARE NO VT_PTR! In VB control works properly, but in VFP gives the same error. Most likely, you have the problem, described in link; the only decision is to write to manufacturer of control and ask him to build control with normal Variant parameter instead of pointer to Variant. Other solution is to build wrapper (in VC++/VB), which will export Variant parameter and internally will work properly with pointer to variant (I can try to create this wrapper in VB, but to determine price I need to have control and look how many properties/methods/events there are (ALL OF THEM must be wrapped independent of using VT_PTR)).