Topband: amp tripping on 160

[WW3S]

After two great nights of being able to receive, I am beyond frustrated, 
as I cannot transmit....something happened recently, and I cannot figure 
it out... I suspect its RFI, but not sure why.....as soon as I transmit 
on my Inverted L, my SPE 1.3KFA amp trips, saying SWRT exceeds 
limits.....yet the SWR displayed is 1.46 to 1......new to me, but not 
new to this season is my tower which holds my Inverted L.....it was 50' 
of Rohn 25, with a Hazer, its now a Alumnatower 48', with a 
wonderpole.......but.....that setup did work, as I worked S9OK and 
3DA0RU with it....I added a second receiving loop in the front yard, so 
thought that was it, but I took those cables out from the shack and 
still have a problem.....yesterday morning, I found the short piece of 
coax had a nick in it, from the mower I guess, so replaced it, and 
shortened my L a bit to bring the SWR a bit further up the band.....I 
tested yesterday morning and it was great, low , mid and high power, 
even 1300 watts of RTTY, no failure, I tried several times during the 
day and all was great until darkness, and as soon as I keyed the amp, 
failure.....I pulled out what little I have left of my hair trying to 
figure this out......the wonderpole is grounded and I "assume" the tower 
is grounded thru that......should I separately ground the tower? Doing 
so will complicate tilting it over, plus I only have copper grounding 
attachments, I thought I read where I shouldn't use dissimilar 
metals.....but willing to try anything to get my 160 TX ability 
back...thoughts?