Well sanke1 my splitter pretty very much installed properly. Using MTNL's Triband since May 2005 so I know how to install it. The reason as also stated by socrates because of increased upload speed the
ADSL line has become very much unstable.
My line stats as in
router are
Line attenuation 31(Down) 10(up)
SNR Margin 12(Down) 10(up)
Data Rate 2048(Down) 1024(up)
whereas earlier before increase in upload speed my line stats were as follows
Line attenuation 22(Down) 10(up)
SNR Margin 25(Down) 25(up)
Data Rate 1184(Down) 256(up)
So this pretty much explains everything. And my telephone is pretty much perfect and actually it's not a normal coaxial cable but a cat 5e lan cable from ground zero to 10 flr. And lan cable is far better than a normal tel. line. Few weeks back MTNL's lineman had checked the line and it was perfectly alright. MTNL has screwed it from there own end.
As a general rule of thumb, if the Line attenuation is greater than the SNR, you are looking at trouble. So yes, there is potential problem with your download SNR being lower than the LA. Someone correct me if I'm wrong but that has been my observation.