In June 2005, a border incident in which more than half of President Museveni's convoy was prevented from entering Rwanda added a disturbing new twist to already precarious relations between the two neighbours.
It was claimed in Rwanda that the Ugandan convoy was carrying more than the permissible number of guns for the trip to Kigali, where Mr Museveni was set to hand over the chairmanship of the Common Market for Eastern and Southern Africa (COMESA) to President Paul Kagame.
Mr Museveni is said to have left the Rwandan capital so upset that, after more than two years now, and despite painstaking efforts already made to boost relations between the two neighbours, the Ugandan leader is yet to make the return trip that would most emphatically legitimise new claims of a comfortable relationship between Uganda and Rwanda.
And now that Mr Kagame has made three trips to Kampala in 2007, most recently attending the Commonwealth Heads of Government Meeting as a guest of his Ugandan counterpart, the pressure will be on Mr Museveni to show that the journey to Kigali does not give him the creeps.
Mr John Bosco Gasasira, a Rwandan political analyst who is also the managing editor of Umuvugizi, a Kigali weekly, told Inside Politics that the Ugandan leader's failure or refusal to visit the Rwandan capital proves that he is a "reluctant" friend of the tiny central African nation. "Here in Rwanda, we ask why the Ugandan president has not recently come to Rwanda," Gasasira said last Saturday, responding to questions from Inside Politics.
"He was invited here for an ICT forum, the Connect Africa summit, and he confirmed his attendance, but he did not come. His not coming here signifies that there is a grudge."
According to Gasasira, "there is a gap which is not yet filled" in relations between Uganda and Rwanda, neighbours that almost went to war in the late 90s over supremacy in the Congolese city of Kisangani.
An informed source in Rwanda, speaking on condition of anonymity because of the sensitivity of the subject, said President Museveni, who visited Kenya and Tanzania during his earlier road tour of countries constituting the East African Community, "should have made the effort to also visit us in Rwanda".
Although it remains unclear whether Mr Museveni will visit Rwanda soon, if he visits at all, Uganda's top diplomat in Rwanda, Mr Richard Kabonero, is said to wish for such a presidential visit, according to the source.
Former Samia Bugwe North MP Aggrey Awori, a keen observer of politics in the
Great Lakes region, said "the initiative [to make a foreign visit] has been on the part of Kigali for their own national interests". Mr Awori told Inside Politics that President Kagame's frequent visits to Uganda have not necessarily meant that he is more enthusiastic about better relations.
"Kigali's interests in Kampala have been for multilateral purposes, and not bilateral," he said, claiming that the Rwandan leader was in Kampala all those times because he had no choice.
In recent times, there have been signs pointing to improved relations between the two neighbours, which have had to work closely on security matters, most recently under the auspices of the American-facilitated Tripartite-Plus Joint Commission.
Yet, even where considerable progress has been made, it has not been hard to see some cracks.
A recent 'bilateral intelligence meeting' was marred by acrimonious accusations coming from either side: Uganda and Rwanda accused each other of illegally holding their innocent nationals in safe houses, according to a reliable source in Kigali, where the meeting was held.
A major sticking point between the two neighbours has been the alleged existence of the People's Redemption Army (PRA), a shadowy rebel outfit that was said to have Rwanda's backing in its insurgency against the Museveni administration.
Kigali has denied the claims and, in return, challenged Ugandan authorities at Uganda, DR Congo and Burundi in the fight against negative forces in the region, to provide evidence of the operational existence of the rebel outfit. And there has also been disagreement over the activities of Congolese rebel leader Laurent Nkunda, whose mission Kigali considers legitimate but whose ways Kampala sees as negative.
But according to Mr Kamali Karegyesa, Rwanda's ambassador to Uganda, Uganda-Rwanda relations are "very good". In a telephone interview over the weekend, the diplomat appeared guarded in his comments, and suggested that the visitation issue does not bother Kigali.
"In our case, President Kagame has been invited and he has honoured the invitations in the three cases [he has visited Kampala]," Mr Karegyesa said. "Indeed, it is a good gesture."