Yes i m using USB rail to power up my MCU. but i dont use a capacitor on MCLR.

I only use a 4k7 resistor connected to USB (+5v) supply.

the strange thing is as i said before, i m using the same circuit i tested on breadboard where it was working fast without any delay on power up.

i double checked crystal capacitors ( 4MHz with 22p farads) they are as stated in the datasheet.

i also checked the voltage coming out from USB, it was 5.6v

the MCLR pin comes to 5.5 volts instantly after attach it to usb as i m using only 4k7 resistor without any capacitor.