[RTTY] RTTY - Slow computer problems

[RLVZ at aol.com]

Hi Guys,
 
I've only been operating RTTY for about 3 years now  and I've still have a 
lot to learn.  I'd appreciate your tips for getting  my CPU to operate 
reasonably fast with RTTY as I've tried several  different Windows XP and Windows 
7 computers and they'll all operate  RTTY fast for awhile... and then 
they'll slow down.
 
Such as, in today's BARTG 75: I'd be decoding and transmitting  at an 
excellent rate and then after a few minutes, my CPU would lock up  while decoding 
and not print for about 10 seconds after his transmission  ended.  Very 
frustrating!  Again, this problem is not new but has  happened with 5 different 
CPU's I've tried over the past 2  years.  (4 Windows XP machines and now my 
new Windows 7)
 
By the way, I'm running N1MM and MMTTY.
 
I've tried different radios and different serial  cables... but the same 
problem over and over: CPU decodes great for awhile and  then "locks up" and 
prints the information about 10 seconds after it's  sent.
 
All ideas appreciated!
 
Thanks-
 
Dick- K9OM