Bad HEX file

uVision has generated a HEX file that it has trouble downloading via ULink. Very occasionally (1 out of 50), it will succeed. Other HEX files work reliably. Regenerating the file does not help. However, when I manually delete a line (record), seemingly any line, from the file, uVision is then able to download the file successfully.
Target is ST uPSD3434.
Can you help?

Thanks,
Richard

IDE-Version:
µVision3 V3.20f
Copyright (c) Keil Elektronik GmbH / Keil Software, Inc. 1995 - 2005

License Information:
Richard Edmonds
Akai Digital
LIC=CZVPR-K7G7L-TWK2Q-L4EQF-ZYPSU-1QV4Y

Tool Version Numbers:
Toolchain Path:    C:\Keil\C51\BIN\ 
C Compiler:         C51.Exe       V8.00
Assembler:          A51.Exe       V8.00
Linker/Locator:     BL51.Exe       V6.00
Librarian:          LIB51.Exe       V4.24
Hex Converter:      OH51.Exe       V2.6
CPU DLL:            S8051.DLL       V3.00
Dialog DLL:         DP51.DLL       V2.46b
Target DLL:         BIN\UL2UPSD.DLL       V2.58
Dialog DLL:         TP51.DLL       V2.45f

Erasing PLD/ACR...
Programming Flash Block 0 (FS0).
Programming Flash Block 1 (FS1).
Programming Flash Block 2 (FS2).
Programming Flash Block 3 (FS3).
Programming Flash Block 4 (FS4).
Programming Flash Block 5 (FS5).
Programming Flash Block 6 (FS6).
Programming Flash Block 7 (FS7).
Programming Flash Boot Block 0 (CSBOOT0).
*** Error: Programming failed.
Total Flash Programming time:  9.0 sec