Run the peripheral clock at 48MHz. It was set to 96MHz which was too fast.

Demo/ARM9_STR91X_IAR/FreeRTOSConfig.h

@@ -47,7 +47,7 @@
 #define configUSE_IDLE_HOOK				0
 #define configUSE_TICK_HOOK				0
 #define configCPU_CLOCK_HZ				( ( unsigned portLONG ) 96000000 )
-#define configCPU_PERIPH_HZ				( ( unsigned portLONG ) 96000000 )
+#define configCPU_PERIPH_HZ				( ( unsigned portLONG ) 48000000 )
 #define configTICK_RATE_HZ				( ( portTickType ) 1000 )
 #define configMAX_PRIORITIES			( ( unsigned portBASE_TYPE ) 5 )
 #define configMINIMAL_STACK_SIZE		( ( unsigned portSHORT ) 180 )

Demo/ARM9_STR91X_IAR/main.c

@@ -228,7 +228,8 @@ static void prvSetupHardware( void )
 	/* FMI Waite States */
 	FMI_Config( FMI_READ_WAIT_STATE_2, FMI_WRITE_WAIT_STATE_0, FMI_PWD_ENABLE, FMI_LVD_ENABLE, FMI_FREQ_HIGH ); 
 
-	/* Configure the FPLL = 96MHz */
+	/* Configure the FPLL = 96MHz, and APB to 48MHz. */
+	SCU_PCLKDivisorConfig( SCU_PCLK_Div2 );
 	SCU_PLLFactorsConfig( 192, 25, 2 ); 
 	SCU_PLLCmd( ENABLE );
 	SCU_MCLKSourceConfig( SCU_MCLK_PLL );