[win32api] problem with file open function -- ERROR_ACCESS_DENIED

 void openFile(HWND hwnd, LPSTR filename) {
 	if (filename == NULL) {
 		OPENFILENAME ofn;		    		/* set up OPENFILENAME structure to be used to initialize the open box */
 		char szFileName[MAX_PATH] = "";
 		
 		ZeroMemory(&ofn, sizeof(ofn));
 		
 		ofn.lStructSize = sizeof(ofn);
 		ofn.hwndOwner = hwnd;
 		ofn.lpstrFilter = "Text Files (*.txt)\0*.txt\0GeekEdit Files (*.gke)\0*.gke\0All Files (*.*)\0*.*\0";
 		ofn.lpstrFile = szFileName;
 		ofn.nMaxFile = MAX_PATH;
 		ofn.Flags = OFN_ENABLESIZING | OFN_FILEMUSTEXIST | OFN_HIDEREADONLY | OFN_PATHMUSTEXIST;
 		ofn.lpstrDefExt = "txt";
 		
 		if (GetOpenFileName(&ofn)) { //try getting a filename with the open dialog...
 			HANDLE hFile = CreateFile(szFileName, GENERIC_READ, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL); //open the specified file
 			if (hFile != INVALID_HANDLE_VALUE) { //if CreateFile() doesn't error out...
 		    	LPSTR txt_from_file = (LPSTR) GlobalAlloc(GPTR, 1024); //text grabbed from file
 				DWORD bytestoread = 1024; //bytes to read from file
 		    	DWORD bytesread; //var that holds bytes actually read
 				//LPSTR curtxt; //current text in edit box
 				//LPSTR newtxt; //new text to put in edit box
 		    	MessageBox(hwnd, "open dialog successful, file open operation successful, variables created and memory allocated for txt_from_file", "dbg msg", MB_OK | MB_ICONINFORMATION);
 		    	RDF: //sorry i had to be evil and have a GOTO. maybe eventually i will replace this with a while loop. anyway, this is the beginning of the code that actually reads 1024 bytes from the file
 		    	if (ReadFile(hFile, &txt_from_file, bytestoread, &bytesread, NULL)) { //if the file is correctly read...
 		    		//curtxt = (LPSTR) GlobalAlloc(GPTR, GetWindowTextLength(GetDlgItem(hwnd, ID_EDIT_CTRL))); //allocate enough memory for curtxt to hold whatever is currently in the edit box
 		    		//GetWindowText(GetDlgItem(hwnd, ID_EDIT_CTRL), curtxt, GetWindowTextLength(GetDlgItem(hwnd, ID_EDIT_CTRL))); //grab the text from the edit box and put it in curtxt
 		    		//MessageBox(hwnd, "memory allocated for curtxt and text grabbed from edit box", "dbg msg", MB_OK | MB_ICONINFORMATION);
 		    		//newtxt = (LPSTR) GlobalAlloc(GPTR, GetWindowTextLength(GetDlgItem(hwnd, ID_EDIT_CTRL))+1025); //allocate enough memory for newtxt to hold whatever is currently in the edit box plus the 1024 bytes to be read from the file, plus the null-termination character
 					//newtxt = curtxt;
 		    		//MessageBox(hwnd, "memory allocated for newtxt and curtxt copied into newtxt", "dbg msg", MB_OK | MB_ICONINFORMATION);
 					//GlobalFree(curtxt);
 		    		//MessageBox(hwnd, "memory previously used by curtxt deleted", "dbg msg", MB_OK | MB_ICONINFORMATION);
 					//strcat(newtxt, txt_from_file);
 		    		//MessageBox(hwnd, "txt_from_file added to newtxt", "dbg msg", MB_OK | MB_ICONINFORMATION);
 		    		//SetWindowText(GetDlgItem(hwnd, ID_EDIT_CTRL), newtxt);
 		    		//MessageBox(hwnd, "edit control text set", "dbg msg", MB_OK | MB_ICONINFORMATION);
 					//GlobalFree(newtxt);
 		    		MessageBox(hwnd, txt_from_file, "dbg msg", MB_OK | MB_ICONINFORMATION);
 		    		LPSTR txt = myGetWndTxt(GetDlgItem(hwnd, ID_EDIT_CTRL));
 		    		SetWindowText(GetDlgItem(hwnd, ID_EDIT_CTRL), strcat(txt, txt_from_file));
 					GlobalFree(txt);
 					if (bytesread != 0) {
 		    			goto RDF; //repeats readfile sequence if EOF not reached. see above note at RDF:
 					}
 				}
 				GlobalFree(txt_from_file);
 				CloseHandle(hFile);
 		    	MessageBox(hwnd, "all done!", "dbg msg", MB_OK | MB_ICONINFORMATION);
 			}
 		}
 	}
 }
 
 LPSTR myGetWndTxt(HWND hwnd) { //i got exasperated b/c GetWindowText doesn't return the text, forcing me to declare a variable, so i wrote this.
 	LPSTR txt = (LPSTR) GlobalAlloc(GPTR, GetWindowTextLength(hwnd));
 	GetWindowText(hwnd, txt, GetWindowTextLength(hwnd));
 	return txt;
 }