For your info, MPLAB 5.00, Picstart + and ICD appear to work OK on an
Entrega (now Xircom) USB-to-Serial interface. 

At first MPLAB greyed-out the USB com port's number, but manually
setting the port number in MPLAB.INI got round this. 
Picstart gives occasional 'cannot receive' errors but seems to be
pretty useable. ICD appears to work fine. 

..Why am I surprised that this worked....????