I've been having issues with this same IE6 failure to fire up, since I upgraded to Spybot S&D 1.5.2.20 yesterday. I'm glad I'm not alone!
I also have Google Toolbar installed, whose Help>About shows version 4.0.1601.4978-big/en-GB (GZEZ)
I use SDHelper, but not Teatimer, and have found that I can enable immunisation as follows:
Firefox
default (Cookies) -
YES
default (Images) -
YES
default (Installations -
YES
default (Popups) -
YES
Internet Explorer (32-bit)
\SOFTWARE (Cookies) -
YES
\SOFTWARE (Domains) -
YES
\SOFTWARE (IPs) -
YES
\SOFTWARE (Plugins) -
YES
Internet Explorer (32/64 bit)
DEFAULT (Cookies) -
YES
DEFAULT (Domains) -
NO
DEFAULT (IPs) -
YES
Administrator (Cookies) -
NO
Administrator (Domains) -
NO
Administrator (IPs) -
NO
myusername (MYPCNAME) (Cookies) -
NO
myusername (MYPCNAME) (Domains) -
NO
myusername (MYPCNAME) (IPs) -
NO
Windows
Global (Hosts) -
YES
If I enable anything marked
YES above, the IE6 browser window will appear fine when attempting to open it. If I enable anything marked
NO above, then I can pretty guarantee NOT to see the browser window if I try to open a link (particularly any links from within email messages).
Other info that might be relevant:
(a) I'm using Windows XP version 2002 SP2 fully patched.
(b) I'm using Internet Explorer version 6.0.2900.2180.xpsp_sp2_gdr.070227-2254 (and have no intention of installing the bloaty IE7 anytime soon, nor going near Vista with a ten-foot-long bargepole!

)
(c) for email, I'm using Mozilla Thunderbird version 2.0.0.12 (20080213) though I am NOT using the Mozilla Firefox browser (unless it is hardwired inside the email client, like IE's browsing guts were, as used by Outlook Express).
I also have no idea whether the settings above are giving me full, or even 'enough' immunisation protection - but at least I can leave these settings on and still operate the browser. Perhaps someone official can let us know whether this is a safer set of settings to use until the main problem has been overcome by a future release of either Google Toolbar or Spybot itself?
I hope this is info useful to someone in the debug process, or in setting it up for their own use! I know I nearly lost my hair until I found this thread and realised it wasn't just me having messed something up in the removal of Spybot S&D 1.4!
Regards
Neil