[vdr] Problem switching channels

[Helmut Auer <helmut@helmutauer.de>]

Hello
Sometimes during zapping it happens that a channel is not shown ( screen is black ).
Then I switch up and down and the channel is here.
e.g. it happens very often when I switch up from SAT1 to RTL or back from SAT1 to ZDF

 >channels.conf:
 >ZDF:11954:h:0:27500:110:120:130:0:28006
 >SAT.1:12480:v:0:27500:1791:1792:34:0:46
 >RTL Television:12188:h:0:27500:163:104:105:0:12003

The problem was also reported on the ltv.boerde newsgroup ( 
news://ltv.boerde.de:119/3CF7F7E3.3010005@writeme.com ), but nobody could help us.
I am currently using vdr 1.0.2 with a "dvb-s rev.1.3", suse 7.3 and a multifeed 
"satanlage"(19,2°+13°) with a multiswitches (8/4).
I have tried several DVB drivers but all are showing the same behaviour.
Any ideas what I can try ?
Helmut Auer